NCF – Extended list of Neutral creatures.

You can never have too many abilities.

Okay. Create a creature with all the abilities in the game and test it ;)
There should be exactly as many abilities as are needed to clearly reveal the creature's idea and tactics. Not more, not less. Jacks of all trades are almost as boring as creatures with no abilities at all.

If a utility accurately determines the strength/level/growth of creatures with abilities, then no matter how many of these abilities there are, the creature will still be balanced.

There is a point here that the utility is unlikely to be able to take into account such things as synergies/anti-synergies. Roughly speaking, the combination of "immunity to blindness," "immunity to mind control," "immunity to berserk," and "immunity to slow" cannot be evaluated simply by summing the value of these abilities: together they are stronger than such a sum, as they eliminate all (or almost all) means of controlling the creature. And it is difficult to evaluate such synergies in any way other than manually, and with experience playing with/against the creature. But anyway, this is a minor problem.