Depends on how you define 'flaw'.
What is the most 'stealthy' man-made thing to fly? The paper airplane, believe it or not. But how many 'flaws' can you find? The word 'flaw' is casually used by detractors/critics if they dislike something and that dislike nearly always depends on their emotional biases rather than objective analyses.
Right now, we do not have any aircraft that can carry bombs like the B-52, have thrust-to-weight ratio like the F-15, can turn like the F-16, and TO/L like an AV-8. That is my criteria and that mean every aircraft in the world is 'flawed'.
So...If the ONLY consideration is low radar observability, then the paper airplane is perfect.
Now...A real flaw is when the US decided to arm the F-4 only with missiles, never mind when those missiles were vulnerable to humidity because that is a technical problem easily remedied, but the notion that guns and air combat maneuvers (ACM) were obsoleted by missiles, hence the US designed the F-4 without guns and pilots went without ACM training. The result for US air power was disastrous.
Fundamentally speaking, what 'flaws' are there in what the Iranians have done? Can it fly? A small scale model proved the shape can exploit aerodynamic forces to its intended goal: flight. Can the model be increased to hold a real pilot and large enough a radar? Yes. Does the design somehow exclude the engine? Of course not, it looks like it can hold a jet engine as it is now. But if the Iranians equip the thing with an AK-47 instead of a Gatling type larger caliber cannon, then compare to other fighters that do carries cannons, that would be a real flaw.
My criticism is about the ease in which the Iranian military trumpets this thing as something significant when nothing is known about it except that a small scale model of it can fly. How would you like it if I call the paper airplane a 'breakthrough' in low radar observability design?