Dude, I feel you. I did a run on Alpha Sapphire recently where I tried to use Pokemon I didn't really use before. Stuff like Breloom, Camerupt, Milotic, that kinda stuff. As a result I tried to have Treecko as my starter and I just could not use him. He was hardly useful in any situation and it felt like he was just... there. I ended up boxing him right after I got his Mega Stone.