What's wrong with making spinoff titles or sequels if they

1) are enjoyable games or movies from a customer's point of view, and
2) SE gets a lot of profit from them?

I'd say that's a good business idea that benefits both sides, the customer and the company. As for the Enix part ruining Square, I don't think so. I didn't really like FFX that much, but I think FFX-2 did all those things well that I disliked about FFX, and, IMHO, added a fun battle system and well designed characters. And recently, Tetsuya Nomura brought us two titles that both seem to be very good quality, Final Fantasy VII: Advent Children and Kingdom Hearts II. Okay, FFVII DoC is supposedly quite so-so, but AFAIK, Square Enix's biggest projects were FFVII AC, KHII and FFXII anyway. I'm not totally sure about FFXII. It seems to be a very good game in some ways, but also very lacking in some areas.

The remakes, while possibly being cashing, are still probably the best versions of the game. Think about FF Dawn of Souls, Final Fantasy III DS and Final Fantasy IV Advance. Final Fantasy XIII doesn't seem all that interesting, though that's just my personal opinion because I'm not overly interested in a futuristic setting. The team working on FF Versus XIII seems quite interesting, though, since many of that team worked in KH and FFVII AC.

Indeed it may feel like SE is cashing out with some of their products they're working on, but I'd say it's better to first wait until they're released and try them out before making any rushed conclusions about them.