Is this guy even worth training?

Just beat the 6th gym and swapped out my Gogoat for a Goomy. But so far he's pretty useless, dying to a few hits and barely dealing any damage in return. He's improved slightly now he's evolved into Sligoo and has an eviolite slapped on him, but he doesn't seem nearly as good as I'd imagined. He needs constantly babysitting.

Is it worth sticking with him, or should I swap him back for Gogoat?