I definitely agree in regards to your synopsis of the difficulties of genre-mixing. It is certainly tough- but to a veteran gamer like myself it is more valuable than gold!
What I was speaking to, though, wasn't genre mixing in and of itself- it was more the idea that you must create a unique, visceral experience in a single player game to get players to buy-in to your product in the long term and therefore recommend it to others- whether publicly or personally to friends.
Players who want to "be the best" as an incentive for playing- and therefore are competitive in nature in that sense-
do benefit from the strategy game layer or the arcade action combat layer in both cases. Crucially, however, that only truly works in competitive games by their very nature of pitting two (hopefully) equal opponents in an equal contest which ideally results in the better player coming out on top (since design indicates there is a "right way" or "optimal way" to play because learning sheds insight into the complexity of said design). That is more aligned with the goals of chess and- admittedly to a lesser extent though it is my favorite strategy game- starcraft (There are some RNG elements there). In a single player game, the designer has to rely on difficulty adjustments through progression and the AI to fill the shoes of a potential rival player. That is practically impossible, imo.
For a single player game: If you want a broad audience, you must accommodate the strategy game element to a point (in order to make replaying the game more fun), but the inherent appeal of your game under those considerations will never appease the types of gamers that are trying to play the game on a competitive-like level, because they will eternally "beat" your design and demand more challenge. The broader audience wants
an experience through having fun while playing and usually digesting- at the very least a setting- and at best a story.
I am ignoring the other category of gamer that has been popularized by the smart phone phenomenon- repetitive "strategy" without a level cap where unique gimmicks are introduced without an apparent overall goal in mind to produce artificial difficulty. I don't buy into that either, to be fair.
*EDIT* *Adjusted for awkward wording or unclear points that didn't have proper clarification*
*EDIT2* typos
sorry!