Anything in particular you have seen in

[left otter]

Generally my impression from the demo was that you're in a good range of complexity for depth delivered although some mechanics were a bit unclear until you play with them. Example: that foil, holo, and polychrome are mutually exclusive. That's hard to discover until you try to add both to a card and stomp one. The design choice seems correct to me, but may benefit from some increased discoverability. That's usually where my discipline (UX) comes in. Ok solution would be to have explanatory text on foil/holo/polychrome, but that likely quickly becomes noisy. Better is something like having a warning tip come up when you select a card for an effect that override something. Best if you can do this without creating an annoying popup confirmation that slows down the player.

Sounds like you're already thinking of complexity reduction, the GDC talk is mostly useful for some specific insight into how ruthless they were in Marvel Snap. I found it instructive, even as someone who is already aligned with the philosophy. If you're looking to layer on game modes, long term progression systems, etc. it's a good reminder of how hard it is to efficiently increase depth without adding an outsize amount of complexity (something that is highly relevant in my day-to-day).