The group finder was designed to, amongst other things, give continuing reason to log in and play to people who would otherwise have no reason to play except for their once a week pass through the high end ops and stabbing Korvik in the face. This change does not affect people using the group finder to create a random pug - it ONLY interferes with premades. I think we can maybe trust people who manged to invite 3 other people to have some clue as to what they invited. And if they don't have a clue a warning rather than an IMPENATRABLE BARRIER TO PLAY is probably more appropriate.
It certainly gives me a reason to keep doing flashpoints.
I know this won't help that much (and I agree with removing the restriction on pre-mades, by the way), but I've had fun pugging flashpoints and helping less experienced players learn the boss strategies, rather than trying to pre-make a full group of 4 for the group finder.
Just last night I took a group of 2 new(ish) players through False Emperor for the first time. They were good at listening and so we made it through with a minimum of fuss and 1-shotted every boss. The new players were super proud at the end of it and I had a good time doing it.