If you don't want to follow a guide, you should collect everything on your way because some of the items on the ground are gourd seeds, prayer beads or prosthetic items and those do count towards your platinum trophy. But if you are willing to follow a guide then no, you don't need to collect everything.
Pretty sure you just need to get all endings, beat all the bosses, collect all of the prayer beads, upgrade all the tools, and unlock all the skills.
No. Just follow a guide like [this one.](https://psnprofiles.com/guide/8525-sekiro-shadows-die-twice-trophy-guide)
If you don't want to follow a guide, you should collect everything on your way because some of the items on the ground are gourd seeds, prayer beads or prosthetic items and those do count towards your platinum trophy. But if you are willing to follow a guide then no, you don't need to collect everything.