If you look at their disadvantages compared to other weapon systems (rockets, shells, bullets, ATGMs etc), there's plenty of flaws to be found
>lower fire rate (a team can operate only a few drones at a time)
>inferior speed (which also means they can be spotted more easily)
>limited payload due to weight limitations
>have to be extra-aware of their surroundings (if they bump into shit they are knocked off balance, which is why they are optimal in open fields)
>can be intercepted by EW (unless they are fyber optic, in which case on the other hand they can get tangled in objects even easier), EMPs, laser etc
>limited range (due to battery life, signal, fyber optic lenght)
>can be shot down more easily due to their lower speed (think multishot or automated systems)
>susceptible to weather (heavy rain, wind, hail etc)
>Kamikaze ones are mono-use, bomber ones highly imprecise
>still by far costlier than shells and ammo and rockets and RPGs
Their main advantages are
>Manoeuvrability
>Versatilty
>Psychological effect (mainly due to their novelty, like gas in ww1)
And that's about it. They certainly have a place in warfare and adjustements will be needed to counter them but are by no means the be all and end all here to replace all other weapon systems as some say.

My bet is that some military at some point will bet too heavily on them while forgetting they can't quite do what shells, rockets, atgms and bullets do.