I really like Valhalla Room, and the ToneBoosters reverb is nice, I use it as an insert on snare sometimes.
Reverb is just a judgement call. Most every mix has some, even the really dry sounding pop stuff. Usually something very short, like a small room ambience. I use longer reverbs on slower material, wider reverbs in sparser mixes, etc.
A lot of it has to do with trends too. Listen to older mixes from the 80's 70's 60's etc. You'll hear quite a range of reverb levels and tones.