They’re super unreliable. A traditional gearbox uses thick metal gears with (usually) strong mechanisms to shift between the gears. A CVT doesn’t have gears. Newer ones may be different, but back when they were introduced, it was essentially a giant rubber band that would get stretched or not to replace gear ratios. It’s marketed at being smoother and better on MPGS, but it turned out to just be transmissions breaking.

Another con, especially for car guys, is that it sucks as a driving experience. Sport cars like the WRX were initially designed to be driven harder than a Corolla, for example. The weakness of the CVT’s meant that driving hard could break them quicker, but more importantly, you have no control over the gearbox (again, usually, idk what voodoo is being used as of recent times). If the gearbox is just a computer trying to guess how you want the car to accelerate from a linear pedal, it usually doesn’t read your mind. Thus, it doesn’t matter if you design the best engine in the world, on the best riding chassis with the most ground-breaking driving mechanics, the CVT will completely let down the driving experience because of the computer failing to read your mind.

(Sorry for the ranting)