What I'm understanding here is that you want Oda to limit himself in terms of ideas.
The goofy designs help make the characters memorable. Same with DF abilities. Also, the earlier designs were very similar looking too. There were a bunch of Zoro and Nami clones (the standard male and female designs at the time), even more than now.
And Blackbeard's ability is still the only one that takes away DF abilities (Haki doesn't do that).
Yes there should be a limit or a level of control because it's like 95% of characters now have height disorders and weird traits. I could handle 50% or even more, but it's become too much in my opinion. I still remember the characters that don't look as goofy like Gin, Kuro, Gan Fall, Lucci, Ace, Marco etc. What makes characters particularly memorable is their input to the plot. I'd rather have a character to remember by their role in the plot as opposed to what they looked like… it's better for the story. There are many more Nami doubles now than there were before. Her body measurements now are ridiculous, almost inhuman. Just because everyone doesn't have a wacky design doesn't mean Oda has to limit his ideas so much. He can focus his ideas more on the plotlines, which have been average by OP standard in my opinion since after the time-skip. Only the flashbacks have been great.
Okay Blackbeard's ability takes away DF abilities, you know what I mean I'm not saying there's no difference between Blackbeard's fruit and haki, I'm saying both neutralise the effect of DF abilities in a fight (whichever way). At one point it was almost as if Blackbeard's fruit was the only way to counter DF abilities. But now how much significance does his fruit hold compared to before?