The game has <10 tracks and tries to stretch the runtime out to like 20 hours and that's almost all that needs to be said.
Everything here is a marked improvement from 3 (because, really, this is a sequel to 3, not revenge) and the challenge events do so much to break up the more immediate monotony, but they all last so long due to the timer reset mechanic and offer zero challenge until you're maybe 10 hours into the game. They also kinda blend into each other when you realise they're all predicated on chaining burnouts for multiplier no matter what you're getting scored on. The races are even more blatantly rubberbanded than ever, your speed doesn't matter, the AI boosts whenever you boost and eventually it just lets you pass. There really isn't anything more than "just don't crash near the finish line" left and it's really, really sad to me. Road rage is still really fun though :D
My recommendation would be to play the first two championships and pretend that that's where the game ends just to avoid the realisation that you will be doing the exact same thing again 5 more times with minimal differences, and that feels like a heartbreaking conclusion to come to with how much I enjoyed those first couple hours.
Maybe if the game's visual direction didn't look like an unplanned collision of Revenge's grunginess and the ps2 realism of 3, I'd cut it more slack? there's really only one track that pulls anything appealing off but I feel like even some basic post-processing could've saved the rest visually. The track design is at least way more distinctive than 3 but seemingly every track has at least one terrible corner where you cross oncoming traffic or get blindsided by traffic below you on an elevation change... which breaks your burnout chain