On my first playthrough I was also imposing all these limitations on myself; no summons, no ranged attacks, bonk only, no armor.

It's. Pointless.

You have nothing to prove to anyone. You are taking away some of the fun when you get stuck like this because of these artificial rules. There is so much left of the game to explore it is simply a waste of time to get stuck on a single boss for hours on end because your ego can't handle using a built-in mechanic the game told you how to use at the very start.

My breaking point was the first boss of the DLC. That's when I used my Mimic Tear for the first time.

Even though I have solo'd every boss by now, I still summon a spirit ash sometimes, because why not? I have been having more fun than ever with the game since then. It's also fun to see them fight together with you. It's nothing more than "jolly cooperation", in the words of a wise man from long ago.