The catchphrase, "if it ain't broke, don't fix it" used to be quite common in the business world, and it was used in the way you just have, as "don't needlessly interfere with something that is tried and true, you're just asking for trouble". I'm hearing it less and less these days, in fact, it appears to be deliberately deprecated. Whenever there's a management shake-up or reorganization everything seems to be turned on its head and done over. It's almost as if the new leadership can't think of what to do so it starts changing things at random, just to put its own mark on everything, and to prove it can. Bring up "If it ain't broke..." at a management meeting or focus group these days and you get a steely-eyed "shut up" look from the "facilitators". Fixing things that ain't broke seems to be an important executive skill these days. The new buzzword is "embrace change".