I see several people complaining about this in this thread. Are you talking about their old interface or the new one they released a couple years ago? I find their new one to be decent. It's a little complicated sometimes, but I think it's hard to build a site that allows you to do so many things without being a little complicated.
The fees will be the same regardless of where you buy Vanguard funds.
The Vanguard UI / UX is absolutely terrible. Opening the website instantly transports me to 2002.