Okay, first let me state upfront that I don't have any data or proof or anything... and most of this is just thoughts and conjecture from observing my son and nephews play games ( videogames, ccg, roleplaying, board and SW miniatures)... but I'm starting to think system mastery might be something the younger generation enjoys and maybe even craves in games.
The RPG you see them playing was intentionally designed to feature system mastery. Anyone you see playing it and enjoying it in the way it was designed to be played and enjoyed can therefore seem as if this is what they wanted and needed all along. But, you note you don't have proof, so...
I know us experienced gamers have a tendency to decry system mastery as an objectively bad thing in roleplaying games... we tend to believe that we shouldn't have to sacrifice effectiveness in one area for aother or that there shouldn't be hidden traps and "not-so-obvious" choices that are objectively better or worse than others... but in observing my son and nephews I am starting to think this is an aspect of gameplay that they, and many of their peers, find enjoyable. Even though old hats may have grown into a dislike of it... is it really an objectively bad thing in game design.
According to this blog by Monte Cook
Ivory Tower Game Design it isn't necessarily always, but it
can be. Of course people find it enjoyable when they figure out better ways of doing things. This is the whole point of building in system mastery - to enable that. The problem is that it turns out that is actually a short-sighted view towards game design.
The "definition" of System Mastery (as given by Monte Cook above) is, "players are rewarded for achieving mastery of the rules and making good choices rather than poor ones." It means that bad choices are INTENTIONALLY provided in the game. So you have players whose game experience is intentionally being trapped and subverted so that others can discover the traps and bad choices and then avoid them themselves. But then what happens when players have played for a while? You have a game that has been filled with BAD OPTIONS that the now-educated players do not want, need, or use. From that point on those sub-optimal choices that were necessary to build in "System Mastery" serve only as a source of COMPLAINT and ridicule. Why weren't the players given a selection of additional USEFUL choices instead of between useful and LAME?
Whether you want it there or not, no matter HOW you design your rules, System Mastery is in fact present in EVERY game. Some choices WILL prove to be better than others. There WILL be reward in the game of success and enjoyment to those who discover those optimal choices. But in older editions the sub-optimal choices were not included as INTENTIONAL TRAPS FOR THE INEXPERIENCED AND UNWARY PLAYER. They were there largely just because at some point, some player or DM had thrown those choices into the mix for WHATEVER reason and they then became part of the rules pile.
When you know the selection of 1st level Magic User spells for 1E AD&D
of course some are going to be more useful than others. But nobody threw the "Push" spell into the mix just so that the player who chooses "Sleep" or "Magic Missile" can feel superior to the schmuck who chose "Push". It is almost certain that somebody at some time actually had a specific use in mind for "Push". It simply turned out that when stacked up as an option against other spell choices it sucked. Or maybe it was simply UNDER-designed/underpowered from the start. In any case it certainly WASN'T thrown in there because it was indeed an UNDER-powered choice - it was thrown in because it was JUST another choice.
My son and his cousins take pleasure in constructing their decks/Star Wars armies/rpg characters/etc. and showing how "awesome" of an entity (for lack of a better all encompasing word) that they have created. They also enjoy the fact that better choices lead to a recognizably better game entity.
And again, a flaw in System Mastery is that until you DO learn the system and weed the crap out of it you have intentionally had that part of your gaming experience subverted. That subversion may even continue as the player who HASN'T learned the tricks of the game is INTENDED to suck just so that the player who HAS learned the tricks can feel superior. Okay, maybe that's not QUITE what was intended - but that is a common practical reality.
And then later still, the players are going to find that having the awesome character build of the hour STILL doesn't win the game for them - in fact, it might only lead to a frustrated, angry DM who has to beat the PC down in an attempt to continue to provide a fun game experience for EVERYONE at the table,
not just the one who has the highest System Mastery.
This competitive build approach also causes them to become more interested in a particular game and it's intricacies in order to better show off their skill in said game. Now yes, I think some of this is due to the competitive factor in most young boys... but I also think most young boys are naturally competitive in some way with most "games"... even if it is a cooperative one. Most kills, highest damage, best items, etc. are all ways they may measure themselves... and games that require system mastery allow them to do this in a way that keeps them engaged and interested... it's one of the reasons I think CCG's were and still are so popular amongst young gamers.
WotC did indeed draw System Mastery and other elements directly from their Pokemon and Magic CCG's. But D&D is not a CCG; it's NOT a game of competition, but of cooperation. In drawing System Mastery from their CCG's they DID start to turn D&D into a game of competition. My build is better than yours, has a flip side - my build SUCKS compared to yours so now I'm frustrated and disappointed just because YOU found a loophole that I didn't.
There's no doubt that there were always elements of competition between players and their PC's, and in fact there's some evidence that some of the elements we came to know as central to the game only derived from players trying to one-up each other. It's a
roleplaying game and that means that such conflict is not just possible it's a
necessary element. System Mastery, however, attempts to set up the game so that there is then an objective WINNER between players. It also then promotes an antagonistic relationship between the DM and the players. Instead of being the instigator and facilitator of imagination and enjoyment for everyone at the table the DM is THE OPPOSITION to the players. If they're not competing against each other the players are competing AGAINST the DM. That is not what the game was supposed to be.