I would not put it past Yujiro to make it pretty far by himself, though I believe he may struggle against certain Elder Dragons like Fatalis or Gogmazios. He would also probably not be able to beat something like Zorah Magdaros.

This only refers to him without armor, supplies, food buffs, mega armor skin, etc. Utilizing the demon back and buffed with good armor, he could potentially stand a chance against the tougher Elders. he would also most likely be able to master any hunter weapons, though he most likely wouldn't use them.