Again, how many buttons would be added relative to what you'd be doing if no challenging dungeon content (or PvP, for that matter) existed. That those buttons see use in M+ does not mean they'd need to be uniquely added just because a game might now have challenging light party content; all but 2-5 per class also see significant use outside of M+.
We don't stop using defensives in raids. We don't stop using immunities in raids. We don't stop using utility in raids. In certain raid encounters, even slows, stuns, roots, stuns, interrupts, and snares can all see use, too.
A raid team in WoW will quite often take Druids, Warriors, Priests, Warlocks, and the like specifically for Leap of Faith, Demonic Gateway, Stampeding Roar, Rallying Cry, etc. Those skills' use are not limited to solely M+. Hell, there have been times when seemingly flavor skills like Mind Control allowed for tremendous advantage in fights or Mind Soothe in readying a council fight room, etc.
Else, we may as well strip the likes of Rescue, Dark Missionary, Heart of Light, Shake it Off, Divine Veil, Passage of Arms, Troubadour, Shield Samba, Tactician, Magic Barrier, Nature's Minne, Warden's Paean, Everlasting Flight, Riddle of Earth, Shadeshift, Third Eye, Bloodbath, Second Wind, Nascent Flash, Intervention, and Oblation, The Blackest Night, and Heart of Corundom's ability to be used on others, etc., etc. They surely couldn't ever see use in any raid encounter after all, right?