Lingering effects need to go away

I cannot stress enough how bad and tedious it is to deal with lingering effects, most of them are straight out bad design at best.
Example : why are some slow effects lingering until you leave the area ? What's the point of slowing down characters with the only way to deal with being leaving the area ?
Another example : volatile plants that are still created and following the character even though the monster is immobilised or dead. This shouldn't exist either.

Please remove these effects that make players feel bad. They serve no positive purpose.