Is it worth to evolve and max out all these?

I have these 100% pokemons. Some with low cp like the Dialga. (Have another Dialga with over 4000 cp and dont have any Dialga candy at all.)
Is it worth to evolve all pokemons to the max and then power them up to max? I mean, most of tjem arent anything I will ever use in fighting😅 Like the Shellos, wont ever use it?
But still kind of special to get them to max?
What do you think? Which ones had you focused on first to power up etc???