Can be fun, but there's a lot to work on
It's good that you made the scaling of atk speed linear in the new update, it was way too strong before, but it leaves a new issue to be fixed. That is, ATK is still exponential (seems to be x1.25 per level?). That means that, at an equal level, upgrading ATK gives you way more value. It's fine at first, but you're really feel it starting at levels 3/4. I'd recommend making ATK's scaling linear, like what you did for ATK speed. Of course, that'll require a lot of rebalancing of enemy HP.
HP and money/kill are also exponential (x1.13 and around x1.3 I think?), and while they don't seem to cuse much issue, I'd argue to make them linear as well, both for future safety (exponentials get out of hand FAST) and for consistency.
One last issue I have with the stats: Currently, Base Stats only matter at first, right? Their gain isn't affected. I'd advise to make base stats a multiplier applied to an universal stat scaling. As in, a pokemon with 1 base ATK would go 1->2->3->4 meanwhile one with 2 base ATK would go 2->4->6->8.
Of course, disregard all that if I'm wrong and the scaling is already affected by bases.
Next, Kill Thresholds
With ATK speed nerfed, it's even more necessary to one shot enemies.
So when you reach a round when you just barely don't one shot, you almost instantly get overrun.
I suggest doubling the atk speed but halving damage dealt across the whole game.
Because in the exemple above, killing in 3 hits instead of 2 hurts less than killing in 2 hits instead of 1.
Second to last remark: Level length
I think 20 waves is way too long for a single level. 10 waves feels way better. Of course, you'd need more input than just mine of that
And a bug I found
The 1000$ on starting a run prestige applies every time you open the main menu. So if you go to the upgrade menu and back, you gain 1000$. Same if you play a level.
Of course, there'll be more to say when the game is properly balanced to push it further, but ironing out the base concept should be the priority.
I wish you good luck