reason why the anime does not compare to quality such as AOT and Death Note and others is that this a extremely long running series, same with One Piece.
It would simply cost way too much money, hence why the movies have a bigger budget as they return much more revenue
Older animes in the 90s and late 80s were mostly hand-drawn hence the detail was more aesthetically pleasing.
Nowadays to save time and ease the manpower it relies heavily on technology.
Successful series such as this could never have it unless they had huge monetary investment.
I like AOT but it won't last as long as Naruto or OP, if it does, watch the quality dramatically decrease