It depends on playing style, if you go for a playing style where you don't bulb techs but settle the GP than i agree that Mids is a great wonder to have since constitution'll take some time and Mids enhances these settled specialists.
But for a bulbing playing style shooting for lib i think Mids are seriously overrated.
I may be missing the point, but I would say that if you bag the Pyramids and run Representation, that should really have a big impact on the strategy you decide upon. You aren't likely to be bulbing all your great people anyway when you get a bonus if you settle them, right?

Would you run Hereditary Rule instead?
I think you should not run massive amounts of specialists in the early game. You need to whip settlers/workers/infra.
Perhaps as a general rule, I don't know. I understand that those things are all vital aspects of the early game, but can't you devote one city to running two early scientists (as well as any other GPs you can run) while you whip stuff in your other cities?
Building Mids without stone is imo more of a losing than a winning option. With stone i think it's more or less worth it unless you cripple your early expansion.
Several others have mentioned that without stone/industrious Pyramids aren't viable, which makes sense. I certainly wouldn't try for them without either of those, but if I get either stone/ind I think that Pyramids are the thing to aim for. In terms of my original post, I'm trying to decide whether a start with stone -> get the 'mids constitutes an easy ride. I'm pretty sure that if you had accelerated wonders
and stone, then you'd be sorted.
Perhaps there were other things that made this game exceptional? Did you get a great start or got a favorable event (the shields one is broken)? I'm not trying to diminish your win ... I'm just saying in my experience Pyramids are just one part of what it takes to pull off that level of win ... and if you did it for your first time ever ... and did it easily as you claim ... then I'd be surprised if you didn't have more than just that going for you.
...
What civ did you use and what strategy did you play? I'm assuming a settled GP SE? Maybe a WE with an industrious leader and marble and stone nearby? Again I'm not trying to discredit you and obviously you know what you're doing but if your first ever Emperor victory was that easy ... maybe you've just really been sandbagging badly all this time.
Don't worry, I'm trying to diminish my win myself! The game I played most recently was with Mao, standard fractal and high seas, normal speed. Capital had stone in the BFC and I chopped the Great Wall. Second city went next to my neighbour Elizabeth, blocking her expansion in my direction. It was all hills and coast but claimed two desert hill golds and one clam. That city built axes and my capital built the 'mids, ran scientists and settled the great spy. Captured London and razed two other cities; London had two corn and two clam so eventually became a GP farm. London (and before National Epic went in London, Beijing) gushed out great people which were settled in Beijing, which eventually received Oxford/Ironworks. However, I didn't decide upon that strategy
until I successfully nabbed the 'mids - from then on it seemed the best thing to do to exploit Representation.
Those cities generated lots of beakers while I backfilled and from then on it was straight-forward. I admit that there were several good aspects to that early game (blocking Elizabeth off, claiming the gold, capturing a great GP farm site, getting the Great Wall too) but of all the things, having stone for the 'mids seemed to be the most fortunate thing and was a significant help in propelling me into a winning position, keeping my science up even with war spending.