I wanted to put some pictures in a thread; I normally upload them to the gallery first. I searched but I didn`t find any threads about gallery problems.
It doesn`t look like anybody`s uploaded anything to the gallery since 2017, I have some vague recollection of putting my pictures on AGO when I was still active there and then linking them to insert here, last time I wanted to put a picture here.
I think it`s old news simply because the capability has been gone from a long time. I`m pretty sure I`ve not been able to add images the entire time I`ve been a member...which matches your 2017 observation.
Like you, I upload pictures to AGO and then link to them here.