Arial is basically a ripoff of Helvetica, except pretty much everything it changes to separate itself makes the font worse. Using it screams “I used Google Docs to make this and I don’t care about typography”.
Yes, that’s a big part of it, but in general it’s just a bunch of tweaks that make it look sloppier (the changes to R and G particularly annoy me). It really is an off-brand Helvetica in pretty much every sense.
