That, right there, is the essence of the big tent - not that each and every one of us will find everything we want - but that each of us can find enough of what we want to still have fun. It is about the essence of the overall experience, not about the details.
And still, 5e cannot give proper support to tactical gameplay. Would you say, in the context of D&D, that sound rules for tactical gameplay are just about the details? Not that I'm personally looking forward to it, but it was promised. And that's the point: in my opinion, a D&D big tent where tactical gameplay is not a real option is not a big tent at all. This is not about supporting an obscure narrative style favored by fans of Dragonlance 5th Age, people who would enjoy some usable flanking rules may well be a silent majority, we may never know.
And, I think they honestly believed that, at the time. I think that was the plan. But no plan survives contact with reality intact. Reality is, they can't produce all those things, but keep the game scope and publication cycle down to sustainable rates.
I agree with that. I'm not asking WotC to deliver on everything, though, I just think they should at least try to deliver something. By now, they're not even trying.
I think, then, that you completely misunderstand what UA is, and what its playtest material represents. It is NOT a statement of where they are going. It is an EXPERIMENT - they demonstrably listen to the playtest feedback, and adjust plans accordingly.
I don't think they're experimenting with UA anymore. The mystic from 3 years ago, the sorcerer that appeared in one of the playtests, those were experiments. For some time now, UA has been mainly about in how many ways they can reflavor/reskin/adapt in a different base class the same set of character options.
Also, related, I think you may have forgotten one of the biggest lessons of RPG history - Do. Not. Split. Your. Audience. Build a game where disparate individuals can go off and play in their little, insular corners, and your audience is split. Each sub-group will expect full support for its little niche, and as we have seen, that's not viable. A successful Big Tent game keeps us all together, rather than sending us off into little sub-groups.
While this has been the generally accepted Ryan Dancey wisdom on the matter for some time now, other publishers have thrived by going in a different route. Personally, I believe the sweet spot is probably somewhere in between TSR releasing a Monster Compendium for Birthright and Jeremy Crawford believing they should not spend 30 pages from a future sourcebook with a psionics subsystem that is not just some subclasses with no underlying connection within the rules.
Here, you say they aren't willing to iterate and innovate, but when they do experiments in UA, you get "worried" about "statements". You do realize that this kind of approach makes it impossible to please you?
If you think the last UA counts as a real experiment, good to you, the same message can be read in different ways by different interlocutors. From my point of view, though, they're not even trying anymore. If this proves to be the best way to make D&D bigger and the Hasbro shareholders richer, good. I can live with that. I don't play D&D exclusively, so I can always look for a different game system whenever I feel like 5e is not checking all the right boxes.
By the way - history: in the time it has taken Pathfinder to get around to doing one major overhaul of its core, D&D has done two. If your takeaway is that Pathfinder is more willing to experiment... well, you take that away, then.
For financial reasons, it seems. Once the cash started flowing in the right direction again, they could not be bothered to release an artificer that's not just a variant spellcaster with a sidebar describing "what's happening in the fiction when you 'cast' your spells".
