Ff already has tab groups. Unless you mean like chrome and then why would you want that. Those tab groups are terrible. Use something like sidebery and you’ll have the best tab experience.
It takes one click to find out that option exists. Two clicks to know where to find it.
I'm not sure I agree with Mozilla's apparent idea that search is the feature they should focus on improving, but I am so tired of seeing the same shallow, knee-jerk reaction every time telemetry is mentioned.
Data can help steer development, and that's not necessarily a bad thing. Mozilla's one of the few entities I believe I can trust with sending anonymized data to help.
Edit: Sorry for the tone above. Though I stand by my main point, IRL frustration leaked into the comment; it shouldn't have.
I would like to understand, what issue(s) do you see with this implementation of telemetry? Regarding opt-out, you would likely have done so already, since it seems to be tied to the pre-existing usage analytics setting.