Question about growlithe line...

I have been playing pokémon FireRed for the first time on switch, and it is really fun. I just caught a growlithe, which is my favorite pokémon as well as arcanine, of course! However, when I checked it's ability, it had flash fire, which I heard is less optimal than intimidate. I would catch another one, but then I would feel like I abandoned it, especially since I already gave it a nickname... I think I got too excited, and didn't think if it intimidated me when I first entered battle. Also, apparently, changing abilities doesn't exist either, in this generation of pokémon games >:p. This post doesn't mean that I think flash fire is bad, but of course, I just heard that intimidate is basically better. I am a casual player for the most part, so take that into consideration, if willing to help. Thanks in advance. :)