If G-d is not limited to our definition of perfection, than we can't even call him in a name, or write on him, because G-d have NO definition, also saying he have no limits is a definition it self .
You are right. The sages stress that there is no definition we can give to G-d to properly describe Him.
That's why we can only use the praises of the prophets, because G-d gave them special permission to use these praises even though at the end of the day, they don't cut the mustard as far as describing G-d. You are right. Nothing could.
If we would come up with our own praises we would never be able to stop. G-d just gave permission for certain praises and said "these are good enough for Me".
All these praises, the "Perfect One", the "Kind One", The "Infinite One" are not proper definitions of G-d at all. We say them to remember that though they do not define Him, he is not lacking these qualities.
For instance, if I say "Dexter is a nice guy", that doesn't define you. Dexter is a person with all kinds of emotions and qualities and kindness is only one of them. You are not limited to only doing nice things.
However, my statement is still true because you are not lacking kindness. It is one of your attributes, but I keep in mind that there is much more to you than that.