The problem is not just trust. If everyone is running the same software then there is a risk of a serious bug that could take down the entire network. With multiple implementations, that risk is limited.
You mean bugs like back in 2010, when someone created 184 Bitcoins? Different implementations might indeed reject those blocks instantly, but if any of the implementations would have a share >50%, it still wouldn't stop it. One way or another, it would need to be fixed and trigger a chain reorganization for anyone who's on the faulty chain, and don't think it's an improvement if different people see different blocks as the most recent ones.
But i expect some pool and cryptocurrency company have their own full node implementation or at least use different publicly available full node implementation (such as bcoin[1] or libbitcoin[2]). That way, some pool would ignore invalid block and simply continue build longest valid chain which prevent the need of reorg. And those who run Bitcoin Core could just execute
as workaround.