While I agree that Transformed is a better game than TSR, there's a lot here that's just wrong. TSR controls the exact same as transformed and has litterally the same mechanical depth in terms of car gameplay as Transformed. Sure, it doesn't have the boat and plane sections but it replaces those with the team mechanics which are really cool (if you play with someone as the game is designed) if unbalanced. The track design is only dull if you play solo races instead of team races. It actually shines in co-op with other people. With that said, Transformed tracks transforming on each lap was fantastic and I definitely miss that aspect.The biggest issue with TSR is the lack of content and that's probably due to lack of budget.
In terms of car gameplay, it's mostly the same yes, but it lacks all of the other modes, and details like the transform boosts, risk boosts and wave-airtime tricks from Transformed, which I think really set it apart in terms of mechanical depth. Pushing your luck with how many tricks you could pull off on a wave, or how close you could get to an object before pulling a way for a risk boost, that was a big part of the excitement in that game. If you go back to the original, instead of those mechanics you had very very fast boost charge while drifting, so you had very effective snaking in S&SAR, they traded that away for more diverse demands on the player across different vehicle types, and that was fun too, but the move to Sonic Racing felt like a step backwards.
It felt like we stepped back to 'cars only' but at the same time, we'd still lost all of the mechanical depth of how those vehicles worked. Snaking was still gone, and there was nothing built into the vehicles to replace it.
I don't think replacing the boat and plane sections with team mechanics offered an equivalent trade off, particularly because the AI are not in my control. If I'm doing well then I'm usually at the front of the race, at which point I don't care what my team mates are doing. Also, the item system just seemed flawed, because if you all just pass items to one another, you endlessly get super meter? It seems it's always better to pass your item than to use it immediately, which to me seems like a fairly problematic design flaw.
Plus, the courses themselves are very simplistic in TSR. So you have all of that mechanical depth stripped away from the core driving, and then you have very straight forward track designs. There are no tracks anywhere near as demanding in TSR as tracks like Burning City Rangers or even a technical but short track like Tree Tops from S&SAR.
Also the car handling is not the same. At least not in my experience, it definitely feels stiffer. The power class in particular feels very stiff and unresponsive. Not like a vehicle with low turning/drifting stats in TSR. This sentiment came up in both previews and reviews too. It's not that they feel explicitely bad, but for someone that spent forever grinding lap times in TSR and S&SAR, I just felt that they felt a little bit worse. Perhaps, because the tracks are never as tight or challenging though.
For what it's worth the game is actually made by a completely different team than TSR, so it's not just differences in budget that give the game a different feel. TSR was made by Sumo Nottingham, and the first two games were made by Sumo in Sheffield.
Either way, I didn't like it as much as the previous two games and I think you have two better kart racers to play on the Switch, CTR and MK8. I felt that Transformed was actually more fun than MK8, at least for me, but TSR doesn't come close to either of those games.
