Regardless of how you feel about the Gunn firing, I think it is a mistake for disney to move forward on Guardians 3. Whether you agree with them or not when the whole cast is ticked off about the change you can pretty much guarantee that they are not going to bring the same effort to the film. Honestly sounds like Bautista would not even do the film. I think that the biggest strength of the MCU is that the actors seem to genuinely enjoy being in their roles and that buys a lot of good will with audiences because that really comes across on screen and makes the movie more fun, I can't imagine that would occur with this film given how the actors seem to feel.
Also before it even starts filming this movie is going to be incredibly divisive, A lot of people who back Gunn are going to hate it no matter what and pick it apart for any flaw they can find, while others will wildly praise the film no matter what as a way to try and celebrate gunn being let go. Honestly Marvel should just hope Hemsworth is willing to come back for 4th Thor movie and combine it with Guardians 3. They could even use the Asgardians of the Galaxy title like the comic that is coming soon from Marvel. Thor interacting with the Guardians in Infinity War was well received and combining the two might minimize the controversy as much as is possible. A fourth Thor movie with Taika directing, that heavily incorporates the Guardians, seems kinda different that just flat out replacing gunn with someone else and might actually lead to a more profitable and better movie than it would have been otherwise.