I think there are a couple of proverbs that might get near the sense of what you're going for:
If it ain't broke, don't fix it
Leave something alone; avoid attempting to correct, fix, or improve what is already sufficient (often with an implication that the attempted improvement is risky and might backfire).
I know it’s an ugly-looking antenna, but you know what they say: If it ain’t broke, don’t fix it.
Also, in computer science, we have the phrase, “premature optimization is the root of all evil”, from Donald Knuth's seminal Art of Computer Programming.
Also, not a proverb, but the concept of the minimum viable product might be helpful. From Wikipedia:
A minimum viable product (MVP) is a product with just enough features to satisfy early customers, and to provide feedback for future product development.