You can become a tremendously consistent winner at all sorts of board games simply by knowing that most local metagames are exploitable, and constantly looking for the exploit. Are players burning their resources too fast, or holding them for too long? Are they undervaluing a resource in one phase and overvaluing it in another? Are they failing to recognize potential resource engines, or building engines to obtain things that can be obtained faster without one? Are they not recognizing or exploiting resource scarcity? Are they failing to recognize situations where they can apply pressure or force actions by threatening to end the game?

Splendor has clever subtle player interaction here which I think is a real strong part of its design.

Good players playing against other good players will often grab one or two cheapies in the midgame to deal with resource scarcity. But you simply cannot win by buying cheap cards, building an engine, and picking up nobles. It's just that much slower.

The metagame in Splendor is more subtle, as you say. It's about clever play interaction and depends heavily on the early-game tableau. Does the tableau strongly favor a single color? Then your choice is to jockey for position on that color, or avoid the resource scarcity and go for weaker and/or less-coordinated cards. Does it have a lot of strong cards? Then it's about finding one or two you can get without someone else tying up your resources. Does it have a lot of weak cards? Then it's about finding ways to gain an upper hand for when the stronger cards come out.

Are players holding a lot of chips? Then you need to avoid getting stuck with a poor "hand" of chips - either a full hand that can't buy anything useful, or an empty hand when the chip supply is weak. Are they hoarding the wilds? That's much like the above, but with even more pitfalls.

Unfortunately, there's a skill ceiling to Splendor, and it's fairly low. Once you approach it, improvement is asymptotic, and the luck element of the game spikes tremendously. These days, I don't really like playing without the expansion. But in good news, the expansion refreshes the game wonderfully.