I mean, ok. Take out "really hard" from the "shoehorns really hard" of my statement. I think the sentiment still applies.
Wizards are limited to the spells in their spellbooks, which they only get to add to on level up and based on how often the DM lets them come across scrolls/others spellbooks/other casters willing to trade or sell access/etc.
So sure, they can switch their complete loadout on a long rest, but only to what is in their books.
For the Bard/Sorc/Warlock they're letting them drop a spell known on a long rest for ANY other spell on their spell lists. That seems like it veers to hard into wizard territory to me.
In the most powerful spells (7th/8th/9th) it really makes your very meaningful and significant choices of spells known at those levels... far less meaningful.
If I can know Wish today and Time Stop tomorrow or Foresight, etc. it doesn't matter that I selected Mass Polymorph with my level up.
8th level it means I can learn Demiplane today, create one store stuff and then just get it back to Dominate Monster tomorrow. Or something like that.
To me, it's just too much flexibility in their spell lists/known which to me should be the silo of the Wizard.
You're also forgetting that the spell lists for each of these are much, much smaller than the Wizard. Yeah, the Wizard is limited by what the DM allows him to find, and by the money he has to scribe the scroll. But he also learns 2 spells per level for his spell book, and 6 at first level, period. Not to mention any spells he may have from his school. That's 44 spells in his spell book at lvl 20, minimum. Lvls 17 through 20, all of them can be lvl 9, which means they have, at minimum, eight lvl 9 spells to choose from every day, and since they can prepare 25 spells a day, they can have all 8 prepared to be used at any time. Yes, only one slot a day, but that's everyone. And anyone who beats Curse of Strahd gets a library with every spell in the game. For a few thousand Gold, the Wizard can know his entire list, which is double the size of anyone else's.
The Bard, on the other hand, will have four lvl 9 spells to choose from. And technically, he could have switched out 4 of his 15 known spells from lvl 17-20 to get al lvl 9 spells, but that's a huge cost against his 15 spells known, all four of which would be competing with that one slot a day. The Sorcerer would have 5 to choose from, and the Warlock will have 5 to choose from. Although, I don't think this would count for the Warlock, as they don't get 9th lvl spells from Pact magic, they get it from Mystic Arcanum, so the Warlock is still outclassed. They will only ever get one 6, 7, 8, and 9th level spell, even with the Spell Versatility.
Also, the Spell Versatility only allows you to switch it for a spell of the same level. That does help. It means, as a Bard, you can pick one lvl 9 spell and just switch it every day, instead of getting rid of your lower level spells to make room for all the 9th lvl spells you may want to cast at any point in time. Which means that these classes will only know one or two lvl 9 spells at any given time, while the Wizard can prepare all of them and not bat an eye.
And don't forget, all these classes except Warlock get Wish, which lets them cast whatever spell they want up to 9th level, from every list. So AGAIN the Warlock gets dumped on. I don't see how letting Bards, Sorcerers and Warlocks switch a spell out every long rest steps on the Wizard's huge advantages.
dnd.wizards.com
