I mean... if you're homebrewing a fix anyway, just make it CR up to the CR of the target or up to half their level if they don't have a CR, to keep its power in line with other spells of that level. If the unbalanced save-or-suck is an issue at your table, give an unwilling target advantage on the save if they're not incapacitated. Unless you rebalance other things, it's just going to mean people won't take/prepare polymorph as much though.

The way you can nerf it, if needed, and still keep it RAW (for those AL DMs out there) is spelled out in the meme. 😁

Either way, let your players know how you're going to run polymorph before they design their character around certain expectations.