With a few notable exceptions, this is literally not true. Just do a survey of all the big money-earning PC MMOs or phone games. Picking a random result from page 1 of the google results for "best selling MMORPGs" - I'll place their list here and comment on it:
Guild Wars: (I worked on this one) heavily story-driven, with a PvP mode. Can confirm lots of time and money was spent on the story content, and we had a competitor that tried to do our thing without the story, and it flopped. We released updates almost entirely made up of authored content and stories every year or so and they made good money.
TERA: Gameplay-focused with lots of story content. Definitely would not have hit without the content.
Planetside 2: One of the exceptions I mentioned - this is just a scaled up multiplayer FPS. (I kind of disagree with classifying this as an MMORPG, but I'm taking this list as it comes).
Black Desert Online: Story focused. Haven't played this one so I can't comment in detail, but I've watched enough gameplay footage to be confident about this.
Star Trek Online: Story focused (with some procedural content). Players are there for the content because they love Star Trek and (in some cases) want to role-play as a Starfleet captain.
EverQuest: Somewhat story focused, but not in the way you'd normally see it now - more like a MUD with some very heavy developer guidance. They literally don't make them like this anymore, though, for good reason.
Rift: Very much in the World of Warcraft mold. If you look at the promotional content on their website, it is clearly story focused even if it has some PvP and cooperative elements.
Lord of the Rings Online: I feel like it shouldn't need to be said, but this game is entirely about story content and roleplay. When a friend of mine interviewed to join that team before getting hired, they quizzed him on the Silmarillion.
Guild Wars 2: Like Guild Wars 1, story driven - probably more so than the original.
EVE Online: One of the exceptions - this game is almost entirely about roleplay, player vs player combat, etc. It's not procedural for the most part though. I'd say this is one of the ones closest to a "metaverse". I should note that CCP tried to go all-in on building a Metaverse out of EVE, releasing tie-in games that shared its universe along with first-person gameplay and character customization... and players soundly rejected all of it, forcing the studio to go back to focusing on the core game.
Runescape: Know almost nothing about this one. Certain it's not procedurally generated, though.
Star Wars The Old Republic: See Star Trek Online and LOTR above. Story driven, very heavy on roleplay. People came to this game for its unique crafted story campaigns for each class, and the studio spun up to build it used the name of EA's leading story game studio (BioWare).
Final Fantasy XIV: Heavily story driven. Story is why people talk about this game. If you look at user reviews or professional reviews, they all mention the story.
Elder Scrolls Online: This might have a good amount of procgen in it, since Bethesda does use that stuff - but my understanding is that this is a story-driven game as well. Could be an exception to the rule, I suppose.
World of Warcraft: The textbook example, presumably why they put it at the end of the list. Wholly story-driven, every major piece of group content has story motivations attached to it and the bosses talk to you. They do things like obliterate parts of the game world and replace it for the purposes of plot.
Games that are "not about content" are a subset of the larger games market, and some of them do make good money. However, even the ones that "aren't about story", like say the latest Call of Duty multiplayer shooter, are still "about content", because they sell you hand-crafted maps to play on and people pay money to get the latest expansion or update with new maps.
Anyone familiar enough with the market knows this. It's okay if you don't, but I would hope investors would do their research before handing money to another "games startup" that's doomed to fail.