If you have a troubled project, and you add more people, you have a bigger troubled project.

It’s a common trap for project managers … and in fact some pretty high brow projects blew up because of this.

When you are called in front of the board, and they say:

“Hey, your project is late, we get it, it’s not your fault, but we have to deliver on the 1st of the month. - and so we’re giving you our 10 best men to get it done”

I can tell you, it takes a certain amount of testicular fortitude to say “That won’t work”. More than I had at the time , in fact.

but it comes at the cost of short term agility

Often long-term agility, as well.

Big teams are faster on straightaways. Small teams go through the corners better. Upgrading from a go-kart to a dragster may just send your project 200mph into a wall. Sometimes a go-kart is really what you need.

“What one programmer can do in one month, two programmers can do in two months.”

Yeah, it happens everywhere, all the time. And the main cause of it is, surprise surprise, people who have no technical understanding of the subject matter.

Currently in a project, where for strategic and unrelated reasons, we ended up with 4 new juniors and had to hand off one senior. In a team that consisted of merely 3 people before.

So, it's just me and another guy having to constantly juggle these juniors to push them back into the right direction and review whatever code they ended up with.
It's so frustrating, because while I'll gladly pass on my knowledge, the project has basically ground to a halt.

There's so many tasks me and the other senior would like to just quickly tackle. Which should just take a few days, no big deal. Oh no, I rarely get a day's worth of work done in two weeks. The rest is just looking after the juniors, who cannot tackle many of the actual crucial tasks.

And it's not even like the juniors are doing a bad job. Frankly, they're doing amazingly for how little support we can give them. But that doesn't stop the project from falling apart.

This, except for bullshit credentials.

You're surprised that gAmErS are complaining about something?

Ideally the solo dev and visionary would cease development and move into a product owner role. Bringing other devs up to speed on the code base while also maintaining quality, vision, and cultivating a team is no trivial task. Not to mention this particular dev may not want or be able to such things.