Yes, also because you would not get a full team in every mission IIRC, so loosing a team memeber meant you had less of a chance to finish the mission.
With regards to Ground Branch, yes they have done "some" stuff to it (two new maps etc.), but I have to agree with you, they are taking way to long. I know there´s at least 5 people working on GB in there spare time. If you compare that to what one guy has done with Black Day since 2017, it really dosent make much sense, well it does, there taking there sweet time about it!
Black Day might not hace MP, but it has a bunch of maps, and as is, it has way more gamplay then GB. Sure it can improve but as I said, still more gameplay then GB, and done with only one guy which also has a family to take care of.