The short answer
Profile → Menu → Settings and privacy → Content preferences → 'Refresh your For You feed'. That's TikTok's native reset button. It wipes your recommendation weights without touching your account, followers, or posts.
For best results, also clear watch history, mark 30–50 unwanted videos as 'Not interested', watch 5–10 niche videos to 100% completion, and follow 10 new accounts in your target niche. Full pivot happens within 24–72 hours.