It's been qualified and nobody has been able to refute it:

1. MMOs need people online all the time by definition. To be massively multiplayer.

Can't argue against the name of the genre, but there are several MMOs which can still be enjoyed solo.

2. Content takes longer to make than to play.

That's true with most, if not all, games.

3. Making frequent content is not financially viable to keep players routinely playing.

But if the same developers making a whole new game out of the blue is financially viable, your statement is inherently flawed.

4. Therefore, content is stretched out, time gated, or padded with grind, all of which are bad things.

That is usually true in MMOs, I'll grant you that. I still hope some out-of-the-box developers will eventually do one that circumvents those.

5. MMOs must be riddled with bad things, therefore the genre is bad.

So, in essence, my main point is that the word "must" in there might be stretching it.

... because the MMO genre is objectively bad.

Jeez. An arrogant and at this point tiresome statement.

It's been qualified and nobody has been able to refute it:

2. Content takes longer to make than to play.
3. Making frequent content is not financially viable to keep players routinely playing.

A MMO does not have to operate soley or perhaps even mostly on content generated by the parent company. The whole point of being massively multiplayer is that you can play with and against creative, unpredictable humans. In my favorite MMOs it is player actions that drive continued player interest with pregenerated content either being a minor part of the game or being completely nonexistent.

Examples:
- In Urban Dead, a human survivor / zombie attacker web game there is no ongoing story or similar content. It is all player vs player. Despite this thousands of players group together to coordinate the assault or defense of key sectors and structures within the doomed city the game takes place in. They have done so for several years with security patrols and recon and well planned, multistage attacks and defenses keeping people coming back for. The Seige of Craiger Mall, an entirely player generated battle where new innovative strategies were employed by both sides, is still legendary many years later.

- In Cyber Nations the basic gameplay of collecting taxes to grow your nation to buy more a powerful military so you can defeat an enemy who is trying to do the same has remained largely unchanged for nearly a decade. The game has zero story and instead runs on player generated treaties, provocations, off site spying, complex economic rebuild plans, and years old grudges. There is no outpacing of the developer generated content here either.

- The spiritual precursor to Cyber Narions was a game called Nation States that had as much or more player generated intrigue but had no grind. Your nation simply grew over time but its size did not matter. There was no military to build or money to manage. Instead battles were based on coordinating the mass unrestrictable movement of players from one alliance to another in order to field enough votes to gain control of that alliance. No grind. No content to run out of.

- In EVE Online there is a thin layer of story but the real draw is the complex functioning economy, the conflicts of player alliances, and the challenge of combined arms warfare with different players playing vastly different roles within even a small fleet. The game has changed much more than the others over its life and certainly people have completed each new piece of the ongoing storylines but I doubt people keep paying for the small amount of story content. Again it's the massively multiplayer part along with the game world that are themselves the draw.

4. Therefore, content is stretched out, time gated, or padded with grind, all of which are bad things.

And if a MMO doesn't run on content updates or new raids or any of that? Also your insistence that grind itself is bad is highly suspect. It was the gameplay mechanics of money earning and resource trades and obtaining a military and rebuilding after a defeat that drew thousands of players from Nation States to Cyber Nations.

5. MMOs must be riddled with bad things, therefore the genre is bad.

No. MMOs can be nearly any shape and size. Grind can be an integral part of the game, can't have a functioning economy without limits on supply and demand for instance, or it can even simply not exist.

Therefore...?