Yeah, I hear what you're saying about the lack of special combo-rules for making more advanced/larger groups in some way. Maybe something could be done with popping multiple groups of the same color in sequence, or maybe give multipliers based on the number of blocks a group clears?
Risk and reward. Best games of these genre has a way to dig oneself into a hole for a bigger reward. Like previously said, I could leave a bunch of blocks out unpopped, but because popping basically means waiting for the right colour/number to come up, it feels one dimensional and has little to do with skill.
I think the player needs more agency or ability to forecast.