First of all, it seems that some of the most enthusiastic fans of Firefox don't really use the browser, because then they will know that the beloved fox icon still exists in Firefox.
As early as 2019, Mozilla updated the logo of its browser, and added the logo of its parent brand (the fox logo after abstraction has become very vague) as the new logo of its broader product portfolio.
Mozilla has also launched a series of small case studies on how this misinformation is spread on the Internet:
The last logo in the screenshot of the tweet with the Firefox logo is actually the logo of Mozilla
Mozilla said that they have no plans to get rid of the fox logo, or never, and the rumors on the Internet are just putting different logos together.
But interestingly, for users of Firefox nightly, the official choice of Mozilla is very casual. For example, we are now using the modification icon of dog: