I'd encourage anyone to try Ring Racers personally. It can feel obtuse - and contary to the game's own website, I'd say that less because it's a 'maximalist' game or whatever other buzzwords the devs have come up with, and just because it can be a little bloated and have some very silly design choices.
But if you're prepared to spend roughly the same time you put learning SRB2Kart's more esoteric aspects in as though you were learning it from scratch again, there's plenty to enjoy. I'd definitely recommend the manual, at least - the tutorial is too bloated and spends a lot of time focused on stuff you won't need as much as it suggests.
If anything, I'd recommend trying it with friends, or a community you trust. While the intent of DRRR's Grand Prix mode was to give folks an introduction to the game before heading online, playing that mode is probably just going to make you loathe the game before you've even had chance to enjoy the genuinely amazing online experience. Weirder still, the "single race" mode is actually fine - it's just the insistence on keeping the rival mechanic and overtuned dynamic difficulty scaling, that means I can't recommend GP to folks wanting to experience the game.
On launch, I only played the game in single player, and I grew overly frustrated at the experience, to an almost comical degree. In hindsight, I went overboard in my criticism (it's why I'm still banned from the Discord) - but at the same time, I also reflect on the whole ordeal and gotta say I wasn't really wrong about the single player either, nor is it a sentiment exclusive to myself.
Even in its current state, it's not the same as trying to beat a route in Ridge Racer 6, or F-Zero GX; both extremely demanding games, but felt like I'd climbed a mountain to the heavens after finally triumphing over them. Ring Racers' single player might as well be you throwing a dart board at the next 20 minutes of your life, and hoping it lands on "an alright time" instead of "I now want to uninstall the game"; there's no satisfaction, no sense of improvement. I don't expect this to change, either.
(If I recall correctly, later patches also made Record Attack easier to unlock - it's a good way to learn the courses, though you can't really learn shortcuts with it)
So my advice? Get some friends, start earning Chao Keys for unlocks (or do the challenges that don't have you playing tons of the GP, if you can help it - I think it's fun doing the challenges, just not when they're tied to a naff mode). Don't worry about 'getting good' as fast as possible or anything - just embrace the chaos, the carnage, the silly old fun that Ring Racers can be. From what I've gathered, tournaments for this game haven't exactly gone swimmingly anyway, so for all the talk of it being a game geared towards player expression and competitiveness, I think the game shines when you're just doing the exact opposite - treating it as a party game, and getting together friends to have a silly old time bashing each other around in go-karts. At the very least, when I've streamed and tried to get people into the game, they've focused their energy into online and had a much better time for it - and I certainly know I have.
For me, GP Mode Ring Racers is a game I simply do not want to play, and online Ring Racers is my current Game of the Year. Even moreso now scripts are dropping to fix some of the smaller annoyances.