When I saw in a YouTube video stating that Naruto was like 40% I was shocked that I had the patience to watch all of that. I think at the time, I wasn't too knowledgeable about fillers since I didn't read Manga, hell maybe I was okay with it in my younger days. It did get ridiculous in the war arc, but at that point I was so invested in the characters that I had to watch it until the end. Luckily these days it seems that more series use better quality animation into less episodes so it doesn't veer too far off into the mundane side stories. I was actually thinking about getting into Bleach so I could catch up, but I think I watched a condensed recap on YouTube or something.
One thing that throws me off is that I don't hear complaints about One Piece having alot of filler which is pretty admirable when you consider how much content they have to work with as well. I just can't get into the goofy proportions.