I'd certainly take passives (especially, involved, mechanics-generating passives) over a recycle of former (and, historically, better) abilities in favor of tack-ons, but I don't think they've seen any reason to start better designing kits. As much as we might complain about certain skills or outcomes, we haven't presented a cohesive view of what would constitute better kits, let alone what capacities could be --or better function as-- passives or what we're unwilling to sacrifice for another expansion's worth of largely tack-on skills.
Though it'd be more productive than consolidation alone if successful (not that we can't have both), asking for "meaningful kit mechanics" is a far harder banner to wave than simply to simply ask the devs to "give us the option to consolidate," and we've already seen the Monkey Paw outcomes of any more general changes to reduce button bloat. I say "harder" because our ideas of what makes for a meaningful mechanic are far more varied than our ideas of button bloat, and even the latter would see very different solutions.
Optional consolidation, though, could help us push that discussion up a step, in discussing what is and is not worth an obligatory separate button, offering us a crowbar for that more complex matter of what are meaningful kit mechanics and how to build around them.
Sorry, I'm sure I've made countless typos and little sense in my stupor by now, so let me just put it more directly:
We have yet to see the devs actively pursue any agenda, outside of response to the most popular points of feedback, to which consolidation would be a worthwhile step. At best, they respond to very specific consolidation requests in isolation, such as per Gnashing Fang before; there is no cohesive design philosophy surrounding such that has been (or is likely to be) revealed to us, be that by actions or direct developer commentary.
Perhaps consolidation, for instance, is something they'd look at doing only if/when it wouldn't leave the job with too little apparent depth; or perhaps it's acted on only if those already popular suggestions coincide with what they wanted to do anyways (e.g., doubling down on all things cartridge), such that they can seem responsive at the same time their cover their asses. We don't know. Without enough actions heading towards it or said commentary, we can't know.
As such, we're left to guess for ourselves whether matters like button efficiency, thematic design, etc., particularly matter to the devs. I do not have the time or wakefulness presently to situate all evidence that comes to mind, but when I consider the changes we've seen over the chain of expansions, I can't help but lean towards "no". Their priorities seem to be solidly on meeting presumed expectations: cool-looking new skills by which to briefly hype expansions, basic and increasingly straightforward capacity increases (seemingly for the nonetheless surface-depth tryhardcore players among us), and maybe a new gimmick or two the weaknesses of which will hopefully take a while to be popularly noted. None among button efficiency, depth, fluidity, identity, etc., are guiding principles; they are merely constraints insofar as a design may otherwise receive backlash.
But what does that mean for us? Simply put, that there is likely no existing momentum towards improved kits, and as such, if we want to see improvements, we'd need to promote certain steps that can be easily communicated and minimally misconstrued that will help situate the design considerations we'd want devs to eventually use regularly and meaningfully. While it might seem an isolated QoL matter, and such can help sell it, consolidation has significant value --and danger-- as a stepping-stone. Just barely behind it lie the questions of engagement through button-flow and button-efficiency, the both of which can meet to examine the quality of how much maximal depth and subjective engagement a kit offers. That can be huge.
But if it gets sold as anything but an option, then we could as easily be welcoming in yet more rarely used, convoluted, and/or "fluff" actions in place of button-flow valuable to some/many/most (a group who --like any other group bounded by a preference-- is hard to measure but whom we can assume, I think, is definitely larger than those who enjoy the likes of AoE|ST fluff actions in present contexts). That's not okay, and what it'd set up would be even less okay.
:: To try to wrap this up, optional consolidation, whether guised only as a QoL feature or in its full sense of both QoL and design scrutiny, can do a lot to push nearer a fruitful conversation about better kit and buttonflow design. It can be a force that would in turn cause other improvements down the line. Other topical changes may do likewise*, but I suspect this is one of the easier --or even the easiest-- of ways to get the ball rolling. If I had any sense that the devs were already pushing towards increased kit scrutiny (beyond the sense of funneling anything and everything towards minimally situational throughput --or, the most direct rDPS contribution possible), I would likely ask that we engage first with the cues and clues the devs are giving us, rather than pushing this policy forward unsupported by favorable contexts. But I see no trace of that. As such, I suspect WE need to start, even if just in some discrete way that can be easily bandied and bannered.
* (A QoL-seeming desire for movement skills like Elusive to check pathing and thereby not --just barely-- throw us off cliffs mid-combat could in turn unlock a plethora of interesting movement skills --set-distance cleaving charges, to-behind-target closers, etc.-- that could eventually reinvigorate the DDR aspects of boss fights, wherefrom others aspects of kit design might then ask for, and try to tap into, that degree or style of "fun", for instance.)
/rant
My apologies for whatever errors I've left here. I will edit this as needed when I am less tired and thereby more lucid, even if we're already pages further along.