There are 3 reasons for Blackbeard downplay
1) Erkan - guy coz of his agenda was able to drive many Z bois against BB just to get under Erkan nerves despite liking BB
2) Power level - Many people don't care about personality characterisation. To them, it's all about power levels and feats.
If you show some godly feats, they will become fan of yours. I mean just look at Kaido fan base - many simply like him coz of his strength and feats. 🤷
It's like they deliberately wanks strong characters with feats...
And, to add, people don't feel much tension with Blackbeard.
This is kind of absurd. I mean Luffy is a yonkou now. He is at top level. How on earth you feel tension when you are almost at your peak? Not to mention, Blackbeard hasn't even got his arc and proper hype yet.
He is still doing what he was doing since Jaya arc.... growing himself
3) Blackbeard portrayal - His portrayal come across as coward. He has been portrayed as a villain - defeated Ace, Law (favourite characters of many) thus hated by many and most importantly, he isn't your typical villain which we have seen so far. Even his looks works against him as he doesn't look badass like kaido or cool like doffy or croc...
But I think he is the best fleshed out character bar SHs in one piece.
He has been portrayed as not some massive monster but there is touch of different sorts of personality traits we humans have.
You gotta see the depth Blackbeard has as a character to like him - coward, cunning, jealousy, determination, zeal, patience, sadness, opportunistic, strength, authoritative and so on....
He and luffy are two sides of same coin.
Where luffy ends up growing as nice kid, BB circumstances drove him to become an evil villain.