MIDDLE AGE interpreted as "phrases with a specific age within them." I've seen several like this before — even published one myself for CrosSynergy — but I like today's progression. Starting with the ICE age, moving to the STONE age, IRON age, and NEW age = fun chronology.

I did wonder about NEW age — SPACE age seemed a more logical progression to me — but there's something to be said about being pleasantly surprised with a changeup. Jules also has a good point, that it's hard to hide SPACE in the middle of a phrase.
Very tough set of themers to construct a grid around. Having four grid-spanning (15-letters long) entries is difficult enough. Then throw in a middle 9, and you're asking for pain. There are so many places in the grid that have to work with at least two themers. Results in such little flexibility, causing trade-offs in so many places. Quite a few rough patches.
Take the bottom left. The biggish corners are going to be particularly hard in a layout like this, so to get a POS, NTSB, OBE, SHEB isn't unexpected, but also isn't great. BISECTS and APEMAN are pretty fun. And Jules did use a smart "cheater square" (to the left of OBE), which I'm sure made filling the corner much easier. But still ...
I won't tick off all the gluey bits, but there was so much that it bogged down my solve. Perhaps something less audacious — three phrases with hidden AGEs, plus MIDDLE AGE — would have been better.
(I would have loved MIDDLE AGE running vertically down the middle of the puzzle, with the various themers intersecting it horizontally. That would have been easier to construct than the layout you see … if you could get the intersections to work. That's always a big if!)
I feel sorry for all you poor saps out there who don't play the world's greatest game, BRIDGE. You probably didn't understand a great clue, [Game for dummies?] — in BRIDGE, one person ends up being the "dummy," the person who plays his/her cards at the direction of partner.
It's a game for dummies, ha!
Perhaps you had to be there.
Some nice bonuses in CINERAMA, MACABRE, even LAERTES for the Shakespeare lovers out there. Those were much appreciated.