Lamenting the decline of one genre while furthering the decline of another seems like quite the severe case of hypocrisy.
There has been no tangible decline of competitive shooters. The first competitive shooters to emerge in the 1990s were typically game modes, or mods, of existing single-player shooters. Quake is the proverbial competitive arena shooter, and it can still be played to this day, as can its sequels and most other games of its ilk and their sequels, such as UT. The original Tribes (a team base defense shooter) can still be played today, and there are active servers available. The competitive arena shooter is perhaps the purest form of multiplayer shooter, and not only are most of the originals still around, but plenty continue to be made. See: Warsow, Reflex.
Counterstrike was originally a Half-Life mod, and as far I'm aware all versions of Counterstrike are still available to play, though most players have moved to Global Offensive of their own volition.
Team Fortress was originally a Half-Life mod, TF2 was a "sequel" to it, and Overwatch will be Blizzard's carbon copy of that specific subgenre. I enjoy playing team base defense games with large, active communities alongside my shooter pals. Natural Selection 2 was one I played fairly recently. If you know of any alternatives, by all means let me know.
Cawwadoody and Halo might be considered decline, but they aren't competitive shooters. They're casual console shooters, and competitive purists never played them in the first place. It's a completely different audience, and no one cares what they do.
A major difference between the decline of RPGs and the appearance of casual kiddie console shooters is that proper old-school RPGs were
replaced by casual, consolized RPGs. There are however still plenty of pure competitive shooters available to play and always have been, whereas we went for years with pure shit in the RPG genre. Most RPGs are played for 50-100 hours and then you're finished with them, thus the problem. In addition, shooters are a much less lofty genre intrinsically.