That's fascinating, given that both the F-15 and F-16 excel at being multirole aircraft. There are no better Gen 4 aircraft in the world.
The F-35 was directly inspired by the extremely successful F-16 design.
So much for those "experts"...
Not saying the experts are correct but some have raised concerns. On the other hand the fact that so many countries are adopting it seems to indicate its detractors may be incorrect.