I have nothing against charging money for a game but the home page says we're supposed to be playing "free games". The fact some players pay necessarily creates imbalance, hence 1/5 for hindered gameplay as a non-payer.
I have wall lvl12, sand bag lvl4, repairer lvl5 and can't get past lvl25 with the henchman. Either decrease the critter's HP or their speed, because it just gets unplayable.