The argument is that there are vocal and influential part of the community who hold tight visegrips to old product
This is common and I agree; however, those folks tend to be people with stable groups that do not want change. I have also noticed that my own appetite for new content, at least in TV and video games, has grown less as I age and I spend more time watching older content.
Of course, that may be because newer content is poor.
Another vocal and influential part of the community who complains about game flaws.
I think this group is diverse but the loudest voices tend to be those who want a different game entirely and want to argue that the game should suit their specific playstyle. Maybe because they cannot find enough people to for their preferred style because D&D is so huge.
I like basic, 1e, 2e, 3e (not 3.5), and 5e because the game can accommodate so many different player and campaign styles. 4e rules locked players into a gamist approach and I detested it. I was vocal about it, at first, then I moved on and eventually quit the hobby for a while after my kids were born.
Then there is ANOTHER group who prioritize new product or conversion of old products. And some fans are parts of multiple factions
So how could you blame WOTC for moving via the mixed signals we give?
I do not blame WOTC, per se, however, they could have achieved the same effect by creating optional sub-systems that were compatible with 5e core.
Hell, I would not have complained, at all, if they added weapon masteries as an optional track. For example, the weapon mastery could be replaced by a permanent +1 to hit and damage or a bonus feat.
That would have provided options for tables and that could have revised the core books to add some of these optional subsystems to enhance styles of play.
It may fragment games but they fragmented anyway because people are now choosing which edition to stick with.
At least with the optional subsystems, they could evaluate to see if most people like one versus another and when 6e arrived, if ever, then move to a new standard.