Inherently flawed?
Absolutely not.
Very susceptible to potential run-out issues, if the design, materials, and/or quality control is poor?
Absolutely.
Good turret presses don't flex much, if even enough to measure.
Crappy, sloppy turret presses, however, are a real problem.
I have messed with or owned Lee, RCBS, Lyman, and Redding turret presses.
My very opinionated rating of all of them:
Lee sucks. Sloppy, rough, poorly designed, and poorly built. But... cheap.
Arguably the easiest turret swaps, though - for people that want to do such.
RCBS's tolerances are not good. Not worth the cost. Not worth the wasted energy. I wouldn't say they're "sloppy", but they still have too much play for my taste.
Lyman's quality control - at least on the presses that I have been able to mess with, and the example that I owned - was very disappointing. Sloppy, floppy, rattle trap with alignment issues.
The Redding T-7 is a solid boat anchor, with tight tolerances and excellent alignment. It's a heavy, over-built chunk of iron. But it comes tight, stays tight, has great leverage, and doesn't flex unless you bend or stretch the bolt holding the turret on (which is a substantial piece of hardware).
I used a Lyman T-Mag II and Redding T-7 side by side, for about 4-5 years. I have always loved the Redding (~12 years, now). I have always hated the Lyman, since my first use of it.
The juxtaposition of two very disparate pieces of equipment made me feel like I had a luxury watch on one end of the bench, and a factory-reject piece of import garbage on the other.
My only real gripe about the Redding T-7 is that the turret bolt is thread-locked at the factory. If you want to be able to swap turrets, you're going to have to apply heat to break it loose the first time, and then clean the threads up.
Luckily for me... I don't swap turrets. I just like being able to leave multiple sets of dies set in the press, while still having 1-3 open stations for small batch reloading.
(I also have multiple single-stage presses available.)