What do you mean by undermined?
All games are approved by the DM before they start so if you want a restrictive game then find a DM who will do that for you.
Organized games also have limits on what is used so no problem there.
If you want restrictive games then run a game yourself.
It all boils down to because you don't like it, then none of us should have it.
Don't buy more books than you plan on using. Don't allow more books than you are comfortable with.
Your reasoning makes no sense what so ever.
Having lots of books puts DMs in an adversarial position where they have to tell their players "no". Even if the DM stated the limits beforehand.
Too many books scares off new players by providing too many choices. The "wall of books" phenomenon, which gets complicated with the eternal "what do I buy next?" question.
Too many books also results in reduced sales as fewer and fewer products are purchased. There's a finite amount of content that can be created and/or used in a game system. When that's reached there's pushing for a renewal and a new edition. This divides the fanbase and causes problems in the community. And making new editions is costly, requiring lots of workhours to create and test.
Demanding books at the expense of the cohesion of many people's groups, new players, and the long term health of the game is, frankly, a little selfish. It's putting personal desires for more reading and game material first. Especially when, based on the surveys, it sounds like the majority of players want fewer books.
For people who like gaming books it's also needless. There's no shortage of books for other systems or past editions to buy and absorb. There's a LOT of truly excellent games to buy with extra disposable cash. In practice, there's little difference between buying a D&D book that I'll never use and buying a Star Wars book. Or Shadows of Esteren. Or a 2e PDF.
I never said I wanted all this in one year.
They aren't even really giving us anything on the side to make up for a lack of books. We don't even have a Dragon or Dungeon Mag. These web articles and such right now are a bit of a joke to be honest.
The problem Wizards' might need to accept is that it wasn't exactly the amount of releases that were the problem, it more about the content in them.
They gave us the Elemental Evil Player's Companion. And the UA are a start. I'm satisfied with that, provided they release some revised versions after more feedback and testing.
And we don't know what's coming down the pipe. A FR campaign setting is almost certainly in the mix, and they've all but confirmed it. And they're almost certainly working on new subclasses, based on demand and vague comments on twitter. So we can expect something. There's no way they'll just have the adventure at GenCon, so we can expect a splatbook of some kind for August of this year.
It's not that they're not releasing content, it's that we don't know for sure that they're planning on releasing the content.