Hey thank you for playing and thank you for the criticism! <3
I agree - the upgrades should be more impactful to make the game scale faster. Very early on it was the opposite, where in 3-4 waves it'd get quite ridiculous (especially with the rubber upgrade, even 1 upgrade would make strafing useless) so we toned it down, though probably too much!
Glad you liked it and thank you again for the feedback!