No, just show more gameplay, that's all

Yes, they are a waste of time and useless to the consumer.

I actually enjoy CGI trailers. They are to me a great way to announce a new game. To get the feel of what's coming, to find out a bit about the story, protagonists, the setting etc. It gives me a cinematic feeling, like watching a movie trailer.
Later on, as the release date nears, sure, use gameplay more, but for the first look at the game, they are perfect.

CGI should not be used anymore at all. We now have the tech to at least have them made using the game engine like Naughty Dog did with Uncharted 4.

Totally agree, not even if accompanied by actual gameplay

The best E3 demonstration is still the live gameplay of Uncharted 2

What in the world would be the purpose of banning it?

Just don't buy games from publishers who lie to you.

Back in the day it was easily discernible to anyone if something was "full CGI", which was called "FMV" for "Full Motion Video" back then.

It's still discernible to people who work in the graphics industry, but the fans are starting to let themselves get tricked more and more often. But no-one's doing anything illegal, and it'd be very difficult in practice to ban and uphold a ban on something like that. It probably wouldn't even give anyone the results they had hoped for, if it meant Blizzard couldn't do their gorgeous cutscenes anymore.

Just don't buy games from liars. Vote with your dollar.

Banned, no, but there should be action against companies implying that a product shown is what a game will look like for a given system. The Batman gameplay for PS4 is actually a worse culprit than some CGI stuff, just because it is implied false advertising. I would wager a class action suit would have success in the US. The Blood borne reveal was completely silly, I'm surprised some were actually excited about that video.

Full CGI commercials should be banned.

Nope.

People should just be able to tell the difference between a CGI trailer/ cutscene and actual videogame gameplay.

You are giving people too much credit.