Honestly? People have a lot of hindsight bias. One Piece, at least "storyline" wise, has pretty much always been fairly consistent. And this includes both the good and the bad.
I swear, people were not around for Enies Lobby. I see people commenting here about how great of an arc it was all the time, and Im telling you that if you read it essentially weekly like me, youd hear mostly the same complaints as Wano:
- Too long (especially in conjunction with Water 7, its the 2nd longest arc in the series, nearly 120 chapters)
- Out of the ass powerups after everyone lost literal hours before.
- Absolutely zero deaths with tons of fakeouts.
- Usopp getting cucked out of a fight
...and so on. And i can also tell you that even aside from all of that, people didnt really bitch and moan the same way they do now, or at least they didnt on APForums. They gave their criticisms and either continued to enjoy the series or just dropped the manga.
Thriller Bark was even "worse" UNTIL the Oars fight started and then ended with Kuma. Marineford only got the praise it did because it showed actual stakes (i.e. death) and showcased a slew of upper characters and their powers (Whitebeard, Marco, Joz, Akainu, Sengoku, Blackbeard and his crew, etc) the likes of which the series had never seen before.
And thats also precicely the problem, people's expectations of this series have changed and grown, almost unfairly in some cases, to pretty high standards.
But imo, pacing truthfully has never changed. What HAS changed is the number of characters. That has has become a problem, even this arc, with essentially 9(!) other focal points aside from Luffy's 10 person crew. Egghead already has 19 (20 if Sentoumaru plays a role) protagonists lol. Thats not including Lucci, Kaku and the whole group Kizaru is bringing.
So yes, what ends up getting sacrificed are core strawhat moments, and imo, this started with Dressrosa, but only really became an issue with Wano. It continues to happen in Egghead. But what has happened is now Oda creates more characters to world build.
Do I think the quality of One Piece has dropped since Dressrosa then? It depends imo. If you value direct Strawhat interactions and moments, then yes it has.
For me, it really hasnt. I have enjoyed the SHF. I have enjoyed the Scabbards personally. I am enjoying the 7 Punks. I spent 10+ years with the crew talking to each other. Im fine with the series taking a more grandiose approach to its world building at this point.
As we near the end, its going to get more intimate. Many of the characters that are left are Pre-TS, and that number will start to tick back down as plotlines are resolved. It honestly has already started to with 2 Yonko assumedly gone.