The saddest thing about modern FE discourse is that it's led to two camps of people fighting over two games that were both heavily flawed and neither deserve the praise that their defenders feel the need to heap upon them so they can make the other side look more wrong.
Three Houses had better characters (excluding Byleth) and better world building, and probably the best main lords the series has ever seen (again, minus Byleth), but the story became strangled and confused thanks to them forcing 4 separate routes and the visuals are just ugly, and the fact that more than half of each of the 4 routes are completely identical is an absolute travesty of bad game design. (I can't believe the developers actually thought that nobody would want to play more than one route.) Also - the monastery sucks, but I did enjoy letting units train their weapon levels between chapters.
Engage had some of the best gameplay in the franchise, actually making changes to the somewhat stale formula that felt fresh and new rather than horribly broken (pair up, here's lookin' at you), but the characters are dull, the character designs were done by a Vtuber artist which was a terrible choice (I know that's subjective and all, but I truly think the art style had a more sever impact on pushing people away than the story did), and the story makes My Little Pony seem like a serious work of literary genius by comparison.
They both suck in truly terrific ways - but if we could get IS to like... take the good parts and marry them, we could have a pretty great next game.