Armenia probably considered it existential. Without material backing of Russia, Armenia is quite literally at the mercy of Azerbaijan and Turkey. Them backing out should be considered huge klaxons for anyone that might have thought it could have been real.
There also was the January 2022 unrests in Kazakhstan, where Russian troops operating under the CSTO framework were used to quell domestic unrest.
The whole thing most likely was the result of an internal power struggle, in the form of real and genuine domestic discontent being used for purposes of the political elite, between former president Nursultan Nazarbayev and current president Kassym-Jomart Tokayev. Whether this was the result of the Nazarbayev faction trying to coup Tokayev, Tokayev trying to purge the vestiges of the Nazarbayev fraction, or a mixture of the two (for example an attempt by the Nazarbayev faction to get Tokayev to agree to some sort of powersharing, with Tokayev using the opportunity and pretext to purge them), is of course something that I don't really know, and don't expect to find publicly available and reliable documents on for quite some time.
Be that as it may, Tokayev certainly relied on CSTO to get Russian troops in (and later out ...) of the country; to him CSTO certainly was real and did matter. Unlike some of the Armenian and Azerbijani actors -- of course not all of
them are fools, but for some of them it is the friendliest adjective I can think of -- he's also no fool. That is one shrewd operator, which should be readily apparent from how he's very successfully used the Russian invastion into Ukraine to solidify Kazakhstans national security situation, and get out of where his biggest patron (one Vladimir Putin) was also the biggest threat to Kazakh sovereignty over their country.
Looking back at how he used those CSTO troops, he also might have known a thing or two how useful individual Russian soldiers were. Kazakh military and police isn't know for their light touch and tender sensibilities in interacting with the public, yet Tokayev used the Russian troops (and that was not without risk to him or his regime) to free up his own forces and use those forces to quell the unrest, instead of using Russian troops directly in that role. One interpretation of this was that while Tokayev certainly is no stranger to the "shoot them" approach of pacification, he also understands that indiscriminately murder is counter-productive, and he didn't trust the Russian troops to refrain from that.
To sum it up, yes, whatever joke it has become now CSTO used to be something that people took seriously. Perhaps not as serious as NATO -- especially in nuclear deterrence -- but serious nonetheless.