So, a trend...one that I have embraced strongly...the DE-meching of 5th edition.
I think it's been subtle, Tyranids notwithstanding (as they've never had true vehicles, and won't, they really didn't lend weight..and they're codex failed to 'balance' a mech-heavy environ), but an omnipresent shift in the FAQ's and Codexes.
Space Wolves led the charge, with the advent of the Thunderwolf Cav and Logan-wing. An army that could compete with fewer and fewer (and even no) vehicles on the board.
Blood Angels, with their DOA and Flying Dreadnoughts.
Dark Eldar, with Beast-packs, webway and Foot-warrior/Wych spam(sometimes relying on disposable vehicles, sometimes not).
Then the FAQ for Dark Angels (making Deathwing and Doublewing very viable, if not top tier).
That last seemed (to me) at first merely a re-dress of a wrongfooted Marine 'dex (the GW gawds couldn't let MARINES languish in ignominy, seriously??)
But the more I think about it, the less I think that the recent FAQ shift (less the Templars, mostly the DA) for our lost Battle Brothers may have been a continuing attempt to re-balance a system that truly lost its footing with the advent of 5th Edition Imperial Guard.
Not for lack of wanting to sell vehicles, but a recognition that single play-style can hurt a system...significantly.
We saw that with 3rd ed...when assault became nearly all, and vehicles (when 3.5 killed assault out of vehicles) fell out of favor. 4th ed put the kibosh on vehicles, and GW compensated later with 5th. 5e SAVED the vehicle...and then IG killed nearly everything else.
Duality units, with cheap and aggressive vehicles toting either cheap, or very effective (sometimes both) units, began to dominate...not merely become potent, but utterly dominate. And melta weapons (and their safe/surprise delivery) became the penultimate weapons.
Now??? well, Melta is important...but I think, becoming a means and less an ends.
I enjoy my Mech, and was pleasantly rewarded with 5e when my Chimera and Rhino (and drop pod) spam suddenly became more vicious, but they then became less fun. I always enjoyed varied methods of play, and the constant 'tin-box' styles began to grate. With SW I began to field no-vehicle lists, and really enjoyed my bugs(hamstrung they may be) when that 'dex came out. BA really ran me up a pole with heavy mech again, but I loved the Baal Predator, and hybridized as well.
Then Deathwing...my poor, poor Deathwing... were dusted off, and brought me full-circle back to min-model count/no-mech FUN.
Grey Knights bring even more possibilities to powerhouse hybridization, if the rumours hold out....
The one thing coming out of this, more and more, is VARIATION. Variation in tourney, in casual play and in combinations that have no unique 'key' to unlock; forcing the need to field take-all-comers lists utilizating variation and mental acuity.
More, now than ever, I think 40k is becoming a thinking game...and less a point and click game.
It'll never be chess, but it is certainly looking less like checkers!