TL;DR: Reddit is removing the option to opt out of ad personalization, targeting ads based on user activity. Some specific ad categories can still be limited, but there’s no more opt-out option.
And the big companies are intentionally breaking their services on clients that give any measure of control back to the users. That should be a blatant anti-trust suit, but they don’t care. Just the cost of doing business if for some reason one of the politicians they own actually takes any action against them.