There is a reason ansible exists and is widely used. Shell scripts are brittle and don't account for a ton of use cases.
For instance- are you going to write a shell script to determine the OS family of a server? Are you then going to do a bunch of if statements for things you want run on Debian hosts vs RedHat ones vs. Alpine? Are you going to manually make templates yourself or just use jinja templates and the template module in ansible (and use variables easily gathered by the setup module)? Are you going to manually select which hosts you're going to target or are you just going to use your ansible inventory that categorizes your machines based on location or purpose or whatever other arbitrary thing and use tags? Are you going to manually dig in and find out how many NICs are in a box, what IPs they have, what CPU, how many cores so you can set some service to use "X" amount of threads, define service templates using those machine variables, etc. etc. etc.? Are you going to make such well defined shell scripts that they can be reused over and over again against a variety of machines without breaking things and make it easy to include them in parent shell scripts?
This is all stuff ansible does quite easily.
It's not the end all be all of course. Some would argue (maybe rightfully) that Puppet or Salt can maintain config drift a bit better. I would argue it's not the tool to use for containerization really either. But it definitely has a real purpose in initial and maintained configuration management and in both cloud and on-prem deployments.