Cleanse probably is, but it's not seen as much because the other spells are easier to use. ANYONE can use Flash that **** is no brainer lol. Heal and Exhaust are also pretty universal: even if it's not optimal for the role or character you are playing, you could fit one of those on and not look silly. Ignite is basically an extra nuke, so ofc casters are gonna use that. Cleanse is a lot more situational than those, and people can fill the role of Cleanse with QSS. That's a big reason, now that QSS went from "lol who gets this" to buffed very viable item. If you need cleanse, 99% of the time you'll just see a QSS in someone's build. Cause now you can open that up to use Exhaust or Heal or X summoner that you can't really find a comparison to in an item (don't say healing reduc for executioners, that's pretty minor)
If you had an Exhaust Item or a Heal item or something like that, or if you could cleanse suppression, you might see it more.