Is there any problems at all if I just keep the legacy format?
achow101 mentioned legacy wallet support will be dropped on Bitcoin Core 27.0[1]. If you decide to use that version in future, you must convert legacy wallet to descriptor wallet.
Also this always sounded more secure to me even if you required to make backups each time you generated new addresses to keep them:
The original Bitcoin Core wallet was a collection of unrelated private keys.
I don't see how it's more secure unless you assume master private key alone could be brute-forced or stolen.
[1]
https://bitcointalk.org/index.php?topic=5469585.msg62962204#msg62962204