not an unfun level at all, but could use a lot of polishing.
so i'm just going to talk about things as i saw them, from beginning to end. to start, we have, well, the start. the player starts slightly off center to the pathway ahead, which isn't a huge problem but it's an easy fix that greatly increases the presentation of the level. don't worry about player 2's spawn, just make player 1 in the middle of the upcoming section. right after that, we have the horseshoe around a waterfall into the first platforming section. the waterfall is neat, my only gripe with it is it's not a water fof so it looks really unnatural. as for the first platforming section, you can barely see where to jump to after the first platform because it's hidden behind the wall you pass. making the player look around is more often than not inferior to leading the players' eyes to the next platform, especially in this situation.
coming into the cave, we have one visual issue already: the entrance to the cave should have some underhang from the previous ceiling to make it look like it's going into the wall. so in other words, the cave's ceiling should be lower than the outside's ceiling so that the player can see a difference in height. while we're talking about visuals, you should use some other textures inside the cave besides gfzflr01 and gfzflr02. on the outside sections you used some flower textures so it looked nice enough, just transfer that kind of floor decoration to the cave. since caves surround the player in a solid floor, solid ceiling, and solid walls, changing up the texture of these will help prevent monotony. look in the "textures" section instead of "flats" for some walls, they have some really nice wall textures just begging to be used in there. other than that, the cave floor looked nice and it was a pleasant short section to connect to the next.
i'll call this next section with the dumb unnamed robo fish the "valley section." this is where i have a problem with the level. visually, it could use a softer gradient back to normal brightness, but there's nothing terrible about it. creativity of design is good too, you're spit out of a cave into a nice open section of a river and a small pond; although you need to look a little for where to go next it actually works well for the section because, among other things, the curvature of the section directs the player well to the spin barrier in the river. however, it's this spin barrier that is the jarring problem. where do amy and fang go? this level is a softlock for nospins, and that is unacceptable level design especially when you don't mention it was built for a certain character to play (like modern sonic level creators mentioning it's a modern level). if there is a path for them, i looked around and could not see it which is just as bad of a problem to have. there needs to be a clear breakable floor that amy and fang can traverse so that they can continue the level. and make sure that it's possible for the entire cast to get out of this breakable floor section as well in case the floor is already broken and another character falls in.
onto the next section (which i will call "lake section"), there's not really much to talk about that i haven't already mentioned. again, the horseshoe is well done with plenty of time to react to the totem poles obstacle at its end, and you use a small cave section to connect into the next section again. i personally think it'd be cool if the totem poles were breakable by strong characters, but either choice is not bad. the main thing i want to direct attention to is the lake itself. i assume you want to punish the player for falling in, but there are way too many enemies in here my man. a better way to punish the player is to just make the lake deeper and leave it be; water is already a punishment for the player in itself because it's slow. this article goes into more detail about how to punish the player with liquids: https://wiki.srb2.org/wiki/User:Toaster/The_(Formerly)_Unwritten_Rules_Of_Level_Design
going into the pyramid section is a little confusing, but the player is never punished so it's not a huge deal. starting with the jump over the spikes, the whirlwind shield is laid out to the player on a silver platter. this usually means the player needs to use it to progress the level, so the player then thinks "i'd better get this and protect it with my life or i'll fail the upcoming section" but in the end it's just another whirlwind. the voided purpose disappoints the player: there is not a cool section that requires the shield, and nor is there any reason for them to have been super careful about losing the shield. just throw this out of the main path so that the player has to go out of their way to get it and it won't seem like it's required for a future section. after that, pretty nice horseshoe but uh oh - what happened to that checkpoint? the easiest way to make a new sector (for the starpost activation in this case) and continue the slope is to brute force it by making a 1 frac unit wide sector, making that sector level to the current level of the slope, and then sloping the rest of the sector behind it. i use this all the time it doesn't leave any noticeable visual traces behind.
now for the pyramid room, that is also a little confusing to the player. first off, the player can't see the crawla commander up top so it's likely they're gonna get hit for no reason. secondly, it's a little hard to see where to go once you reach the top of the pyramid, mainly because it's not in the direction the player is likely moving. the best way i can put this in words is: the player sees the stairs and goes up them, but they can't see anything in front of them. having to make them stop at the top of the pyramid and search for the cave entrance halts the momentum of the level, and makes the player frustrated. remember that horseshoe section into the totem poles? that was good because the player couldn't see and then suddenly had to react to an obstacle. this should follow the same pattern (NOT because the pattern was established earlier, it's just good design to reward the player): the player can't see coming up these stairs, so the jump should be straight ahead of them so that they have to react and jump to it.
and finally, the last stretch of the final cave section is way too long for no reason. it's just 5 seconds of awkward running while being surrounded by GFZFLR02 - not the most appealing design. at the end you have the player jump over some snail lasers, you should use more obstacles like that for a straightaway section. i'm not saying you should flood the corridor with snails either, you should find similar challenges where the player needs to jump over danger and then put those inside so that it's not just pressing forward like you're playing sonic forces.
one thing that bothers me with the level overall is how thin it is. it feels really claustrophobic, especially with the high walls looming over you. levels with this "canyon design" aren't bad practice at all, but they need to be surrounded by a nice, open area - look at gfz2, it pulls off "canyon design" very well. the level is always surrounded by walls, but the actual playing field is big enough to feel open - and sometimes even includes these walls you were initially surrounded by.
you use horseshoe sections typically very well, and the way you transfer the player from section to section is typically well done and exciting. just be careful to not place unreactable danger where the player can't see it. you use your creativity well and have a lot of potential to make some great maps, keep it up.
The level was pretty short is sweet. Your banik placements are alright and the map is just one sided, very thin and impossible to not find the goal like mario. Overall the map is fun, Nothing to hate about it.