If all I get is an address hash, does that mean I can't get all wallet addresses from electrumx?
Not directly in terms of calculate the input out of the resulting hash.
But in this case you could just create a list of
all addresses and their hash. Then lookup the hash in your table and you got the corresponding address.
[...] It seems that electrumx stores scripthash, but I want to get all the wallet addresses, a lot of BTC explorer How did they get the wallet address?
Block explorer run a full node (e.g. bitcoin core) with
txindex=1 and some custom software to query the needed data.
They most likely don't run an electrum server. There is no obvious reason to do so.