Why didn't they fire Ian Goldberg and Andrew Chambliss years ago?

I'm not trying to insult Fear The Walking Dead, I somewhat enjoy it for some entertainment value, and I wish the showrunners the best of luck with whatever they do now that the show is finishing.

But I've been wondering for a long time, why didn't Scott Gimple or AMC or someone fire those 2 after the terrible trainwrecks of season 4 and 5? What would the actual reason for keeping them on be, after such bad critical reception of those seasons? And now the ratings have just gone down and most people agree the show continued to be bad if not worse with them in charge.

They had already done the same thing previously, by firing Dave Erickson after season 3, despite most people agreeing the first 3 seasons were much better than the rest of the series and season 3 is usually cited as the best (so his firing made no sense. Another thing I'm curious about.)

I understand if Erickon didn't want to come back after they "massacred his boy", but couldn't they find someone else to steer the ship back on course after Goldberg and Chambliss proved they weren't able to make a good show out of it?