Why games can have lots and be uninteresting
What exactly is something interesting?
Firstly, lets get an idea for what it means to be an interesting game. Games have a toolkit of Skinner boxes which are environments of semi-random, semi-predictable stimulus that punish and reward the rats in the box. It's this stimulus and semi-random reward which is the only meaningful difference between a slot machine and a box with a lever. If you remove this, you make the "game"... playing a box with a lever, fundamentally uninteresting.
As a result you get bored. Boredom being a natural response to being unproductive in the animal brain, as you'd have to be engaging with the world and taking in stimulus to be productive(or at least it related very heavily).
Lets look at a games which remove a lot of stimulus. Chess and Go. They do not have these arbitrary rewards. There's no reward for winning, there's only the combinatoric explosion of the moves the units can make, and how interesting they are.
This combinatoric explosion can be likened to John Conways' Game of Life, where you have rules that seem chaotic, but produce interesting results that build up... gliders... glider guns etc...
So this game, which is to say "play within an environment with constrained rules", gives back a lot more than the rules we put in, AND, those rules will often enough mirror some understanding about the world. A game about light and shadows, will reflect understanding about the universe in terms of light and shadow. A game about portals, will reflect understanding about the universe in terms of spatial manipulation.
So if you fully remove the skinner box and other manipulation methods(and that's what they are, there's no other way to mince words about it)... you're just exploiting the players... whether they're aware of it or if they enjoy it, doesn't relate to its benefit or negative(after all, a drug addict enjoys their drug while they are on it, but that doesn't relate to its benefit or negative).
An interesting combinatoric explosion? That's pretty easy to make right?
I... would disagree, and I will use mathematics to present my point.
With the axioms of mathematics, you can then produce a lot of propositions... proofs which you can build up in interesting ways, like proving Fermat's Last Theorem and so on. Each one of these steps(while difficult for the uninitiated) is very interesting and has interesting ramifications and ripples and once you snap one proposition, more seem to prop up by its combination with previous propositions. So this here, is what I'd consider the "interesting" combinatoric explosion, where each new combination unveils some unique or interesting "truth" about the game or the system.
On the other hand, you have the uninteresting combinatoric explosion. So you get 1+1=2, that's interesting right? Then you get 2+1=3. Ok... so it builds up, that's also interesting. But continuing it on forever? That is only as interesting as adding 105453+1=105454... which is pretty far from being interesting.
A somewhat less ridiculous form of this happens in most games, so you have this rather uninteresting combinatorial explosion- and where the interesting parts exist their designers don't really explore its ramifications very much. Of course they are made appealing, despite being ultimately *boring* games at their most fundamental level. Using the idea of boredom, these games subvert boredom very well, but they also subvert all the feelings you have from being well satisfied or understanding things better... so you do not feel productive either. As a result, it favours numbness over feeling productive or unproductive which in my opinion is worse than either form.
It's worth noting also, that this is concerning games as an artistic or interesting medium. Games as a sport require an interesting base that also does not collapse down to "one optimal solution" and some skill in their execution. This lack of an interesting base, and this collapse down to one optimal solution, is probably why a lot of competitive games have short lifespans. Counter Strike, Super Smash Bros and Mario speedrunning are the various examples where this isn't the case, and they are interesting and don't have one optimal solution and enough of a skill component to be good games even in their 90s-00s early raw states.
Additionally, I think... that a smaller amount of "objects" with a great amount of *interesting* combinations(can be seen of as viable Chess "lines" and "sequences") is also beneficial here, as it means there's less to pollute the actually interesting elements. I don't think Super Smash Bros Ultimate will stick around a long time, because it's polluted by a lot of playable characters, and some "echo" or duplicate characters which are slightly different usually as a crutch(Lucina and Marth differences is pretty much just that Marth requires more precision which itself is interesting, much like precision in a game of Basketball).
Summary
So I conclude that games that have lots of options, pollute their *interesting* options(Elden Ring, Looter Shooters, most RPGs, etc), but also that the interesting options don't combine much and aren't really *that* interesting to begin with when you remove all their "juice".
The reason why this is important, is there's not much more you can do in "juice" once you've got it down pretty good. Plenty of Genres have died(a subjective term I use to describe that few new *notable* games of its type are released) as a result of this. RTS Games, Fighting Games, Racing Games all fit the bill for this type of game. This is because the addition of interesting ideas *is* synonymous with the innovation people talk about. The other reason why to care about this, is because I think games should respect the player as intelligent actor, and not resort to *disrespecting* the player in terms of their time. That said... it's almost impossible to navigate games without feeling disrespected- it's akin to the disrespect Disney have towards Star Wars and Marvel fans.
This is also why I believe this notion that "everyone has an idea about how to make a game but production is king" is actually a half-truth. If you can produce a game, you can produce one, and it'll be condemned to mediocrity. This is because most ideas are not rich ideas. The same thing is said of other mediums and other industries. Once you have the execution down and can do that well... the hard bit is actually finding a good idea(exploring it is usually easy because you're just in a design discussion with the "universe" and teasing out all the "propositions" and "proofs" that follow from the idea).