no.
but it depends.
"install" means to have the program embedded all over the system.
track and car mods can be deleted like that, im 99.9% sure.
other mods and addons - no.
advice: do not use installable stuff - its badware 99.9% of the time.
note: bad is not malitious, but its pretty close.

uhh ohh i want MrDeap back...

Anways generally, practically "yes". Most mods only install in one place and removing them will clear 98% of it. Whats the 2% then? Stuff like replays that include the mod, laptimes, setups, and cached stuff, like the special vao shaders that get downloaded from a repository when you run the mod (cm has whole section dedicated to vao patches).
In practice such residue takes little space and does not interact with other things, so it can be left alone... So it really depends on WHY you are deleting stuff.

- If its for space, then yeah just delete then main folder.
- If you dont want it to show up in the list you can "turn off" mods which will move them to another directory where they will be dormant. With symlinks (windows feature) you can even point that directory to another (storage) drive to save space.
- If the mod *broke* something, then its a hassle. You have to look into the original packed mod file and see its directory structure and uncover where its putting its files. In such case the mod will probably have files that land elswhere and causing trouble. They need to be manually fisned out or replaced back by original (by for example running steam file verification).