The only time I've allowed a PC respec was when 5E EE Companion came out and our human barbarian felt the goliath was a better fit for what he wanted his character to be. I had no issues with it, because I had already decided to reskin the goliath as half-giant in my campaign. Ergo, his already tall human became a shortish half-giant (and obviously changed some mechanics).
I also allowed players to switch out spells and cantrips when EE Companion and VGtM came out, but in both instances the players decided not to until they were normally allowed to do so in game.
I also allowed players to switch out spells and cantrips when EE Companion and VGtM came out, but in both instances the players decided not to until they were normally allowed to do so in game.