Login to other user failed

I have problem, I have rocky server, i go attack to my oracle user, and i limited the user by:
1- sudo usermod -s /sbin/nologin oracle

2- by change permission to set of tools in /bin/ to 750.
like su top find ping ping6 traceroute traceroute6 nc host nslookup dig wireshark tcpdump nmap whois top bash sh dash zsh fish tcsh csh ls dir cat ifconfig ip echo

3- deny all outbound traffic except ssh

Now, I revert all permissions to the 755 and give the user login access by
sudo usermod -s /bin/bash oracle

but still can’t access it. I need help because i want to backup the database urgently.

this message appear:
su oracle
su: failed to execute /bin/bash: Permission denied

You are doing the su oracle as root?

What is the output of namei -l /bin/bash?