I tend to lose interest if I'm just left out in the open with no directions, so a degree of linearity is essential for me. This also applies to things like the World of Ruin where I almost ended up dropping FF VI because I felt overwhelmed by all the options I had without any strong indication as to where to go first. Most open games however manage to avoid this issue in some form or another. FF X-2 and XII for instance did a good job at that.

On the other hand I've never really felt like strongly linear games actually suffered from their linearity in particular. The problems generally lie elsewhere.

The Mi'ihen Highroad is actually one of my favorite examples of linearity not feeling constraining There's something to do and find every single screen including an optional aeon fight, lore, talking with several named side characters, a boss fight where winning is optional, exploring with a chocobo, and it tops it all off with the completely optional Oldroad.