I actually disagree with this.
Whilst you are correct that 4v4 tdm is barely a thing, and you're right more should be done to try and get these games up and running, actually denying duel to new players won't really help that situation.
Secondly, ELO-hell doesn't really exist in the same way in 1v1. If you are better than your opponent, more likely than no you will win. ELO hell is more of a problem in team games as you can't rely on low-skill teammates, which is why people playing CS:GO whine so much.
Lastly duel is an important part of Reflex. It's the gamemode people see in the fragmovies and in the tournaments. Certainly it was the former, watching cpm fragmovies that got me into the gae in the first place.