The threat that North Korea poses to the rest of the world has also been minimized partly as a result of its isolation (whether self-imposed or otherwise). To the extent that the Russian economy deteriorates through isolation, its reduced ability to wage conventional war is a benefit in and of itself.

Agreed, but North Korea's isolation hasn't helped topple the regime nor improve the lives of the people living there.

While probably true, the current goal is to help the people of Ukraine. Helping the Russian people may be a good goal once this job’s complete (although I’m not sure what the current overall Russian sentiment is toward the situation).

Each situation is different.

I wouldn't support 75 years of isolation in Russia, but a country in free fall might lead to regime change in the not-too-distant-future. I want Putin out. I can see scenarios by which he's out in weeks, months, or a few years.

Even more, I want Lukashenko out before Belarus is a nuclear power. Right now, we could affect regime change without nuclear consequences. That option leaves the table soon.

The dictator of North Korea is protected as a useful tool for China. Is Russia willing to submit to Chinese control if they have no other options?

Or with Cuba. In fact, has it ever helped?

Yeah it did help. They have a crippled economy.

That only made it harder for the people there to topple the regime or have better lives.