I don't really think this is true. I've seen some obscene damage out of powerstanced greatswords and colossal weapons, especially in PvP. There's a lot of great strength weapons, especially if you're willing to spec a secondary stat like Int or Faith. I played a primarily Int character, but for Int scaling melee, so I feel like I got a good bit of the strength build experience using the moonlight greatsword, and it was fun.
https://youtube.com/watch?v=dayf6ZSdcg8
I really don't understand how people are saying the fights are balanced around having a summon. In my experience, every fight except Maliketh, Malenia, and Elden Beast gets turned to easy mode if you use an upgraded summon. The fights are definitely balanced for solo play, and I had the most fun playing solo, except for Godskin Duo. I summoned Bernahl and a spirit ash for them, beat them on the first try, and I don't feel an ounce of regret lol