After finally getting the acorns to drop, I think my main critique is they're too random. I felt frustrated and completely stuck because I ended up with a rookie I couldn't evolve because of lack of exp... And the acorns just. Wouldn't show up. Consider maybe a higher spawn rate? At least when you haven't unlocked that mode yet, as it makes it much more possible to actually evolve what feel like dead end mons when first starting out, which could def drive people off, I think.