Indeed.
To add to that, in any other MegaMan game there's the advantage of no fewer than 8 upgrades being unavoidable; try beating MM1 without Super Arm. Or 8 without Thunder Claw. Or MM&B without Ice Wall. In X6, NOTHING is required. Literally. There are always multiple solutions and never is one single item necessary, but absolutely nothing in the game short of Falcon Armor is unavoidable either. You know what we call that? Open. Some people just can't handle it.
When were we given the option to cap our charge level? 'cuz I missed that.
I was talking about the X series exclusively, where one doesn't really need the use of any upgrade to advance normally, except for X6. While it's true that you don't need the use of any one single item exclusively, the fact is that you still need one. Or two, in some cases. I have no issue with the open gameplay... but it isn't perfect. I still think you shouldn't have the need of any part whatsoever. If it were as open as you say, then there would be the option of no upgrades whatsoever.
As for the charging in X1, it's called shooting before it hits the last charge point, which isn't too difficult. Leads to some less than intuitive moments at times (I tend to like having my charge ready at all times), but it is doable.