Seem, I always defended the game just based on "linear isnt bad", not really thinking about the reasons why its linear.
Ive also always been confused why FFX is well liked despite... also being very linear up until it opens up at the end? But XIII got memed for hallways???
I've always defended FF13's linearity as being totally normal and not at all strange for the series. Seriously - in FF7 you have some "pit stops" that you can explore, but by and large you have to do everything in the game in a pretty specific order until Disc 3 opens up the whole map to you. Same thing in FF8, 9, and 10 - FFX-2 and FF12 were exceptions to the series' gameplay, and both of those games would get criticized for having too much side content at the time, which might explain why Squeenix would look to course correct away from that style.
The difference in practical terms between FF13's structure and classic Final Fantasy is more or less that the classic FFs all had "potemkin open worlds" that you could run around in but not do much in until the endgame, and FF13 doesn't bother with that.
That said FF13's writing is still awful. And the gameplay sucked too. That was the year that FF14 1.0 launched, and we know that it took like a decade for FF15 to come out, so I think it's safe to say that Squeenix was going through some shit at the time.
Personally, I defend the gameplay as deeper then its seems on the surface level as someone else summarized better than I can elsewhere in the thread.
As for the writing, the overall plot is kind of a mess but as I've mentioned a few times in this thread I'll defend the character writing as some of my favorite in the series till my dying breath. Its a good ensemble piece with some good character development. It works for me.