I ran a 1-17 game and typically as a DM I wasn’t consistently dealing over 20 damage per attack until I was using CR 13 or greater monsters or higher, and I’d typically prefer several monsters per encounter to one, so that probably happened consistently around the time the party were level 12 ish, and even beyond that, I would say I generally didn’t focus on massive damage output because knocking PCs out the fight in 1-2 rounds doesn’t give them enough time to assess the battle and then deprives them of agency through a particularly slow segment of the game.

I’m currently a player, playing a trickery cleric 9 rogue 2 and loving it, but I think I use my 4th or 5th level spell slots for a damaging spell about once every 5 encounters, because those spell slots are better for exciting spells like polymorph, scrying or modify memory, or at least I find those more exciting than making my number go high. In that game, the paladin 6 bard 5 may on occasion do a spike of damage via a smite but his spellcasting is also primarily utility too, and our only massive damage dealer is our draconic sorcerer. A lot of our consistent damage comes from our barbarian who is probably putting out 40 damage per round but rarely over 20 in a hit when not critting.

As players, if we want to knock an enemy out of concentration, we’re more likely to pepper them with small secondary attacks, forcing them to make 3+ DC 10 saving throws per round, which has generally been more successful than one 30 damage attack and a one DC 15 save, just because of how the odds fall.