Some of the things a reverb on the sum tackles can also be fixed by other means, with fewer side-effects.

If you have a very dry mix and a reverb would have raised the noise floor a little to get rid of unintended bits of complete silence (which might be quite common in sparse intros or outros), then you could use some other quiet, non-distinct sound to achieve the same thing (noise, field recording, that sort of thing) and restrict it to the places where it's needed.

If your sum reverb is used to put everything in the same room, then my question is, why wasn't it already? Fix that in the mix—be very conservative with the amount of different reverbs and delays you use.

As always with music, there are multiple ways to skin a particular cat.

It will make many things so much easier for you. If you're asking, is it worth the time investment to learn: yes, it absolutely is.