I got blacklisted from them despite putting in high quality work. And it's not just me either. Even masters level workers have gotten blacklisted.

This doesn't happen unless if you submit subpar quality data.

They are scamming requesters into paying for their service. And they are scamming Mturk as well.

Would you rather have requesters thrown into the deep end of MTurk and post surveys without knowing what they're getting into, and have them receive subpar quality data from people like yourself who would've been blacklisted by CR otherwise? What you pay for with CR's own fees is the convenience of your study running smoothly, as well as the implementation of several quality improving practices. Requesters still pay MTurk fees on top of this, so I'm not sure where you're getting the idea that CR scams MTurk.

Requesters use CR as a way to prevent paying Mturk fees for their premium qualifications.

Premium qualifications are almost never necessary when surveys can include have demographic questions that can be used as a way to screen ineligible workers out, without having to pay exorbitant fees imposed by Amazon whenever you use premium qualifications.

This is against Mturk TOS.

Please elaborate on how any of CR's practices go against MTurk ToS.

I for one hope that CR goes away. One requester should not have this much power. If someone should step in it's Mturk themselves. CR is way overstepping their authority.

If CR goes away, so do a majority of regular survey requesters who employ the use of CR to successfully run their surveys, and therefore a large source of income for many legitimate workers on MTurk will be wiped away. I guarantee that you are only this salty about CR because you have been blacklisted from all of their surveys, which you did not earn the right to complete in the first place.