If Avalice's intent was to make a level that could have seen the light of day in actual 2.0, my opinion is that he failed. Most standard levels throughout SRB2's history have had alternate paths and plenty of rings (enough to obtain and maintain Super status in even the toughest of stages if you play your cards right).
Doomship throws all of that under the bus in favor of a strictly linear enemy gauntlet. Older versions only had four(!) rings, and they were all at the start; you at least get rings at every checkpoint in this version. However, there are massive gaps between checkpoints - there just aren't enough of them. Plus, you won't find any monitors with powerups in them - no shields, no speed sneakers, no invincibility. Any of those would have helped make the level feel like less of a slog.
The frustration of Doomship spikes depending on what enemies are in the room with you. Getting cornered by a Sharp or Jetti-syn is
not fun. What makes it worse is that the enemies are their 2.0 variants. SRB2 enemies from older versions often lacked sound cues that make it easier to tell when they're attacking or vulnerable. The old version of the Spincushion, the Sharp, suffers the most from this, as it's missing two key sound effects: the "bumper" SFX that plays when it rebounds off a wall, and the "cooldown" SFX that plays when it returns to its blue docile state.
However, having a bunch of BS enemies doesn't translate to actual difficulty here. The enemies alone aren't likely to kill you if you can just recollect your rings in time, since there's shockingly few ways to permanently lose your rings for what would have been a late-game level in 2.0. This is because, outside of certain parts such as the yoku blocks and the ejection sequences, most of the actual platforming is rather tame. There somehow aren't enough environmental hazards, and most of the ones that are there are simple to avoid, even if you can't fly.
And then there's some parts that either weren't thought out correctly or tested well enough. The first ejection sequence has no delay between pressing the button and forcing you into space, giving you no time to react. The second ejection sequence, despite having a huge delay, doesn't give any indication that you
need to react because the end of the tunnel doesn't open until you physically reach it. In older versions it was possible to get crushed in the size restoration pod, because the pod locked your controls but didn't stop your momentum. The room that floods with water lets you kill the enemies that would otherwise be a huge problem...
before triggering the flood. (At least one person thinks the last one is intentional, though. I can't tell.)
What pains me is that there's some good stuff in the level too, although it's mostly visual. The GFZ and CEZ dioramas, the long connector bridges, and the massive rotating cannon are all great setpieces. I can tell that Avalice loves version 2.0, and in these rare cases, that love shines.
But to get to any of that, you have to trudge through the beginning. I don't care if it's 2.0 accurate, it just sucks. To start, you're immediately thrust into a forced combat section with Sharps and Robo-Hoods. This isn't a first-person shooter, it's a platformer. You shouldn't make rooms where the player has no choice but to fight enemies to proceed. That's not me talking,
it says so on the wiki. Then there's two more Sharps in a tight space where you're shrunk, making them near-impossible to avoid, plus a random chunk of ground falls to reveal a pit.
And after that there's the first ejection sequence, which again, gives you no time to react and will give you an undeserved death.
That's when I called it quits the first time - it's one of the worst openings to a level I've ever seen. It's so incredibly hostile and poorly thought-out; it feels like I'm being slapped in the face for even trying to play it.
Avalice's Doomship Act 2 wouldn't have been accepted into 2.0 had it been made back then. It ignores so many crucial level design principles, past and present. Yet I gave it two stars instead of one because there are flashes of genius in Avalice's work. I know he can make something better, but he's holding himself back. He's stuck obsessing over the past, when he should be thinking about the possibilities of the present and future.