An attraction's quality is in the eye of the beholder, specifically, the average guest. If an attraction is high quality, usually the average guest wants to ride it, be it a high-quality spinner or a high-quality themed coaster. So, given that you can't say that quality and popularity are mutually exclusive, perhaps all that can be said about 7DMT is that it is high-quality in terms of construction practices (and maybe not even that just based on appearances.) Superstar limo was probably high-quality in terms of building a safe/low-maintenance ride system . . . but artistic quality varies a lot based on perceptions of different people.
When people describe 7DMT as being "not an E Ticket", they are also making quality judgements which may, or may not, turn out to be true. You can blow the budget of Splash Mountain on an attraction which doesn't turned to be as popular as you might have liked, and alternatively, a "sleeper" attraction can turn out to be quite popular. So, all you can say about an attraction under construction is that it has such and such a budget, and may turn out to be popular, to one degree or another.
The whole "D" versus "E" debate is kind of meaningless for 7DMT, as it implies a level of percision that doesn't exist because it is based on subjective assessments. E-Ticket is kinda used as slang, an imprecise term that should perhaps be avoided when trying to differentiate an attraction such as between a D and E. Of course, wel all know that a "real E-Ticket ride" is also slang for a great ride.
So, for a 3 year old, Dumbo might well be an E-Ticket, though adults would probably disagree.