Older MMOs, like Guild Wars 1, Everquest...Ultima Online...Asheron's Call...even going as "new" as City of Heroes (and WoW while has a cash shop, is definitely not the focus)...
Those MMOs all have one thing in common (amongst of similar MMOs released in that time frame)...they were made by developers with passion and love.
These days, developers make MMOs to make as much money as they possibly can. They focus so heavily on the cash shop (GW2 for example very heavily focuses on the cash shop, but GW1 did not at all) and RNG loot boxes and pay to win schemes that there is no love anymore. Developers only focus on making as much money as possible. That is fine to have money, but older MMOs were made by developers who loved MMOs and wanted to make a game THEY loved and they hoped others loved it too.
Is this one reason so many MMOs are failing? No passion is being made with them anymore? WoW came out and while it has a cash shop (don't think it always did, did it?) I feel it was the last MMO made with passion and love. And funny enough, it was also the last successful and biggest MMO.
Since then, all I see is such a focus on cash shop and barely any love for the game...in fact...most MMOs are built AROUND the cash shop and heavily focus on it. But I see little love for the MMO itself only existing for the purpose of the cash shop. No passion or love being put into their games.
If an MMO was to be successful, it should be made by developers who love MMOs and have passion for them. Not developers looking for a quick buck. And sure its not guaranteed to be liked, but at least its made with love and developers who actually love MMOs.
My Skyrim, Fallout 4, Starbound and WoW + other game mods at MODDB: