This is the core issue (not with this particular update, which is disappointing for most people, but in general with updates): There isn't a set of cars that "people want", because there's so many different groups of people playing the game who want different things from it. For every person who wants all the new GT3 cars, there's a different person who want classic GT1s, and there's a different person who wants all the BMW Ms, and there's a different person who wants all the Skylines back, and there's a different person who loves the meme cars and wants more of them. And so on and so forth.
The community is not a hivemind who want certain specific cars, and I have no idea how PD can cater to all the different groups of the playerbase.
There are cars that definitely stand out when it comes to wishlists, as they show up nearly everywhere though.
Of all those examples you gave, one stands out, the meme cars. First, before those cars were released, no one thought of them as good additions. Second even if the idea of "meme car" came from the community (which it didn't), players would think of other things to add instead of a Jimny or Alphard. Things like a Batmobile, KITT for example. Or the Ariel Atom for the Clarkson meme.
Then you have the "quirky" cars, which can be almost anything. From a pace car, to an RS6 Avant, to a LCC Rocket, Lotus Carlton, etc. If you want a quirky van, most players would go for one of the fast Transits or the Espace F1.
Want an ambulance? Most players would rather have the F1 medical vehicles like the C55 AMG, one of the C63 AMG (all of these are wagons), the DBX-707 (fast SUV), or the MotoGP M3 Touring Safety Car. Any of these could do the job as "the ambulance of GT7". Even the EVO 9MR Wagon safety car from the Ebisu circuit could do the trick. The livery editor does the "ambulancing".
And as SUVs go, people asking for any of them, surely didn't have the Jimny in their mind, with plenty of fast SUVs on the market to choose from. Another example of PD doing the opposite of what the fanbase asks.
I agree, that it's hard to please everyone, but atleast you should make an effort. PD saw the great reception that the Spec II cars got. Did they look at it and thought "Great, they loved all the cars in the update! Let's not do that again!"?
It's not that hard to figure out what to prioritise. BMW M's? Start with
any M5, the new M4 CSL, the M8 Competition (the closest thing BMW has to a supercar). AMG? AMG One, SL65 Black Series (or any SL AMG), SLS Black Series, any E63 AMG, a more modern A45/CLA45... The GT3 roster needs some updates? 488 GT3, Vantage GT3, Continental GT3, C8 Corvette GT3... They could complete the roster of 2019 DTM cars, by just adding two others (the BMW and the Aston). Prioritising is the key here. It's just sometimes PD chooses to steer away from what's requested, and adds something completely different.