It is a good observation.
Also one could ask himself what is the measure of maturity?
One could be time, then you have to consider that the welding rod was invented by Kjelberg in the 1890s, so by this concept FCAWs are not mature at all.
Another could be manufacturers, then you would observe that welding rods manufacturers exist in the world by the hundreds, but FCAW manufacturers only by the dozen (at least independent ones) so could be considered not mature.
Another concept would be use, then you could verify that in the last decade FCAW use has multplied itself many times over and rod use has gone down.
Everything depends on the criteria used.
All indicates it is growing much more than the quantity of worlwide manufacturers.
So it must be a good business, dont you think ;-)