getnewaddress won't generate bech32 or p2sh-segwit addresses
The problem is that your wallet version is extremely old - it predates support for compressed public keys (which was added in v0.6.0, released in March 2012). As segwit addresses require compressed public keys, Bitcoin Core is failing with the keys you have, and defaulting to legacy addresses instead.

The solution is restart with -upgradewallet (just once), which will update the wallet to the latest version but break compatibility with old Bitcoin Core versions. Note that you'll need a new backup after doing so.