Is it worth using CleanMyMac X in 2021?

I would not allow that stuff within 10 miles of any of my Macs.

The possible problems: Big Sur has its own built in protection which means your OS and associated files are sequestered in a read only, otherwise non-accessible volume - neither you nor any "cleaning" app has access to it. So, it is completely unnecessary and may cause havoc trying to access the OS/files.

AlexanderLG wrote:

What do you guys think, should I try it out?

Stay away from CMMX, "As if it were a swarm of bees."

Well, having 30 tabs open is "stressful" for any consumer grade computer. Depending on use, browser, resource hogging apps, etc. 16 GB is considered minimum these days. You also need to keep plenty of empty space available for the processor and OS to be able to function properly. I empty cache and history every time I shut down - cleans out a lot of stuff. Also, rebooting after that cleans up unnecessary stuff.

Additionally, yours is 6 years old and - sadly - has outdated hardware (processor, etc). Mine is a 2017 with 16 GB RAM; I maintain 200 GB empty because I do some movie/image processing which requires a lot of empty space for rendering. Mine is as fast as it was originally.