If you read into Web.Com, yes, they are quickly becoming a monopoly on host companies. They do not disclose many of the hosting companies they now own.
If you can find a company that allows clients to install Let's Encrypt Certs on shared hosting, please let me know.
Yeah, fair point. I have not used shared hosting for a long time now (static sites are easy/free to host, and dynamic ones don't play well with shared hosting), so I didn't know the Web.com story.
I used DreamHost in the past and they had a configuration option in their control panel to automatically install and maintain a Let's Encrypt certificate on your behalf [1]. If you are stuck with Web.com you may consider using a reverse proxy/CDN such as CloudFlare.
It's shady, but technically not price-fixing unless they are a monopoly. You are free to take your business to somewhere else.