That is the business of any game designer, is it not? In fact, if you're not doing this, I doubt you're doing your best work.
Historically, no. That has not been the prevailing concept of how to design an RPG for a wide market -- and it is most thoroughly against the D&D tradition.
Flexibility has been very much to the point of RPGs. It's not just "okay" but
encouraged to change things to taste. The published framework is not the end but the beginning of creativity.
D&D campaigns have included such an array of elaborations that if some novelty in the field was not first tried there, then it was almost certainly adopted by one group or another. Critical hits and attacks of opportunity, "realistic" combat and "comic book" combat, spell points and free casting, monster characters and special powers, customized classes and lists of skills, rules (particular or abstract) for social and economic activities ... these and many more go back to the 1970s.
The key is that none of those were incumbent on everyone. There was a very basic set of core rules, easily added to, subtracted from, or modified to taste. That was good because different people had different tastes.
Chivalry & Sorcery, on the other hand, was a very complex system that to a notable extent forced on players the designers' view of what a fantasy game ought to be: a rather "realistic" medieval European world with a Tolkien influence, and magic reflecting the designers' interpretation of real-world magical beliefs. It was not nearly as successful in the market as
Dungeons & Dragons, Tunnels & Trolls, RuneQuest or
The Fantasy Trip.
Part of what has happened to D&D is a shift in philosophy, selecting for a demographic of players keen on having everything "officially" spelled out. Unfortunately, things are spelled out in such complex and holistic fashion that it's a real bear to modify the game. If one does not like dissociated mechanics, or any other aspect of the new Credo of Fun, it has become much better simply to choose a different game.
There are other designs that could easily be made to play much like 4E; but 4E does not exhibit reciprocal flexibility. Even before considering the many particular reversals of D&D tradition, that general and fundamental one looms large.
Some people want more rules for non-combat activities. Some of those want more abstract, dissociated rules; some want more rules with verisimilitude. Then there are people who want fewer rules, and find it inconvenient to strip away existing ones because they are so integrated with the whole.
The same variety of desires exists relating to combat -- and old-style games made it very easy to cater to different tastes.