I think Satisfactory hits a few of these targets, if you haven't already tried it. The amount of resources is determined by a map that is not procedurally generated, so there is a hard cap to your resources per minute, though the resources never run out. So end game focuses more on playing efficiently rather than brute expansion.
I second this, it's what OP is asking for. Word of warning though: this game is hard as hell. It reached a point where I'd spend 2 hours on a level, realize I messed up and can't salvage this, and gave up. I never got really far.
I thought SpaceChem uses the same mechanic as Opus Magnum where the benefit of optimization is just the player's place on the histogram. I'm looking for more interaction between machines than that.
Maybe Techtonica? It just came out on Gamepass. It's like Satisfactory but in a cave and you can't just build anywhere... honestly, it's just another factory game though.
You play Dyson Sphere Program yet? It'll scratch a lot of itches. Riftbreaker was pretty fun as well. A little meh at the higher levels though.
I think I actually know exactly what you're looking for. Factoryidle (.com) is a "idle" game but is very involved and nuanced. As you progress you get small expansions to your factory floor space but the real boost in productivity comes from upgrades that make things more efficient. Each upgrade impacts different resources, thus changing your optimal ratios and forcing you to redesign the factory several times to be be optimal. I will say that a downside of this "build better not bigger" game philosophy is that it's basically been solved as there are community made factory layouts that can't be beaten
Shapez looks like it has the same problem as factorio, where expanding outwards is always possible and easier than micro-optimizations. That's not the kind of gameplay I'm looking for.