I feel the same way. They ignored almost ALL of the Old school comments in the surveys in lieu of listening to PF, 3e and 4e players, and it shows in the final document.
They never actually released the results of any of the surveys, just commented on them very selectively.
It's easy to fill out a survey, never see the compiled results, and conclude from the way the survey-taker acts on those hidden results that they're pointedly ignoring your opinions and focusing on contrary ones, perhaps even arbitrarily or because of their own prejudices.
Ask a 3.x/PF 4e/E fan, and they'll probably say that the modern fans' concerns were ignored and 5e caters to the grognards.
As a grognard fan of 1e who also liked 3.x & 4e, I look at 5e and see a lot of 2e influence. ;P
However, there were some items that were particularly LOUDLY discussed online, which had people wanting things done with 5e, but instead of those showing up, the exact opposite happened at times.
Other times they went with the crowds' shouting. DoaM, for instance.
I've said it multiple times recently, but I actually decided to do just that with 5e, and DID create a document that does just that on DMs guild (called 5e Old school). I think that shows that 5e IS highly malleable and adaptable to other editions and even the older editions right back to the original...but that's my opinion and my take on the matter.
Especially the older editions, which were very DM-driven the way 5e is, and very open to variants, and not mechanically tight or balanced. You could even make-over 5e to be more and more 3.5/PF-like, but the payoff is slight - you can just use PF, it's already there, it's very well-supported, and anyone can pick up support if Paizo ever slacks off, because it's all OGL/SRD.
I think what may have happened in regards to the modularity was what I mentioned above, WotC realized that a majority of their audience was not going to come from the older edition players (despite that the numbers of these players outnumber the others at a 4 or 5 to 1 ratio...most are either too preoccupied with other interests these days like family, or will only play the older editions rather than playing a new 5e edition)
I can't agree with that. WotC has been chasing the lapsed player from the 80s almost since the moment it took over the D&D franchise. 3.0 proudly declared 'back to the dungeon.' Classic 80s adventures were constantly being reprised. The Red Box came back with Essentials. 5e has gotten review after review likening it to AD&D or 2e.
And, anecdotal evidence warning, I see guys at my FLGS on a weekly basis whom I used to see maybe once a year at a convention. I'm not the oldest guy running D&D there, anymore. Returning players are a very real thing with 5e. It might or might not be succeeding at bringing back the fad years to WotC/Hasbro's satisfaction, but it's doin' something right.
and instead a majority of those taking the surveys and participating in the playtest were those who were familiar with 3e, PF, and 4e.
I think the surveys were probably, ultimately, filled out by a fairly small proportion of gamers. I was one of 'em - I kept filling out those surveys to the bitter end. But, I was all but alone in that among the 40-60 gamers who frequented our FLGS. I could dragoon maybe a half-dozen of them at a time into playing at my playtest table, but, even when they had definite opinions, they wouldn't bother with the surveys.
But, ultimately, 5e /did/ deliver modularity. The basic pdf has the same 4 basic classes as 0D&D w/Greyhawk. The class designs are more prolific than 2e, but very much in the 2e model. 3.x MCing/feats are optional. All the classes in the classic game, and in the 3e PH1 are represented. You can pick & choose what you want, to a degree, even as a player. The DMG
has modules that edge the game in other directions.