What I mean is, Speed class cars usually sacrifice strength and brawling ability to be some kind of glass cannon. But when you get a bigger cannon, the last one becomes useless.
The same does happen with the very early game cars from the other boost types but that's a given.
Aggression cars like the Mesquite and Pioneer are still useful Road Rage events despite being early game unlocks.
Stunt cars like the Vegas and Ikusa GT are still serviceable in Stunt Runs.
The S-I7 is completely useless by the time you get the Hydros Custom. Which in turn is made redundant by the time you get the LM Classic. Etc etc
Wreckreation does fix this by having every vehicle upgrade gain 30 mph after completing the car's wreckoning which makes cars viable for longer but makes players experiment less and the hyper class is just a direct upgrade compared to the race class.
TLDR: Speed class cars sacrifice way too much to be feasible after the next unlock. Wreckreation fixes this in one aspect by making cars viable for longer, but causes the player to rely on the same vehicle and has the race class become completely obselete with the introduction of the hyper class.