I think it's pretty obvious that over time, class mechanics have been simplified so that players can easily choose which "skin" (job) they want to play and not have to worry much about how to play that class as they are all relatively the same based on what role (dps/heal/tank) that they perform.

Some classes have a bit more uniqueness than others but even still, the differences between classes have diminished.

The simplifying of classes has even been addressed by Yoshi P. Yoshi has stated that "streamlining" the classes was a priority for 7.0, although it's been happening gradually anyway over the years.

Here is a link to the live letter from the producer where he speaks on this specifically: https://www.youtube.com/live/oh5piV-0MWQ?t=7145s

In the video he states classes will begin to become more unique by version 8.0. Who knows if that will happen or what that will look like but if you were on the fence as to whether classes were losing their identity or not, hopefully hearing it from the director and producer of the game is proof enough.