I'm honestly mixed about this debate. While I do agree some dubs are god awful (4kids is definitely a prime example) some dubs actually hit their mark, however it feels like it isn't great nowadays.
Dubs from 90's anime were actually pretty bad, not in the sense that scripts were changed, but the voice actors felt like they rarely put any emotion into their voice. In my honest opinion, Cowboy Bebop was one of the only few 90's dubs that was excellent. If we're gonna look at some of the blockbuster anime from the 90's, such as Dragon Ball Z and Sailor Moon, the dubs for those shows were pretty bad. In fact, I despised Sailor Moon's original dub.
Of course, as the years progressed, dubs started to get better, with solid performances in anime such as FullMetal Alchemist, Code Geass, Ghost in the Shell, the list can go on. As of 2016-2017 the only new dubs I can tolerate were Your Lie in April (which hit me really hard) and JoJo's Bizarre Adventure (yes I'm a JoJo fan, but I can point out stuff that subs did way better in dub and vice versa) and it genuinely feels like most dubs are pretty weak (don't get me started with Attack on Titan)
To kinda sum up, while dubs weren't perfect, most of them are manageable, but it does feel like dub quality is taking a turn for the worse, as most dubbed characters feel like their English voice doesn't really match up with the character, or just sound downright awful. Hopefully things will improve, but really that's all for time to tell.