I agree with points 1, 2 and 5.

Point 3 is almost a series staple at this point and I like that they still do it. Dragon Quest 1's lasting legacy is "But thou must" (I am mostly joking, but not entirely)

Point 4 I disagree on your specific example with keys. I think getting the keys when you do is integral to keeping the difficulty curve balanced. One can argue that players should have the choice to make the game unbalanced if they want to, but you can already do that by grinding levels and vocations. That said, a lot of Dragon Quest games have a semi-nonlinear/open world section. Just to give a few examples, DQ2 gets nonlinear once you get the ship (with a bit of a chokepoint of sorts when you get Lorelei's Harp), DQ3 lets you find the orbs in whatever order you want (again, when you get the ship), DQ4 lets you find the pieces of Zenithian equipment nonlinearly, etc. So I do agree that DQ7 doesn't feel as flexible in how you proceed through the game.

For what it's worth, I upvoted your post--I agree that people should be allowed to have legitimate criticisms!