Any one of the factors, including human psychology (aka not wanting to be alone for years on end and possible death)

They wouldn't be alone, and people are already plainly willing to endure that risk, as being an astronaut is probably amongst the most highly sought after professions. ISS missions already last six months. It's a major challenge. It is in no sense, however, a hard limit that "debunks" the idea.

radiation levels

Shielding.

Also since the moon landing, there have been very few advancements in terms of human space endeavors. Obviously it's because there just isn't the funding nor the desire to do it. Human achievement isn't some linear progression where we get better every decade. There needs to be some motivating factor.

I did say "when countries have had the appetite". You can't rule out public favorability for decades to come.

Even living on Greenland due to global warming is 1000 times safer and more realist then Mars.

We're talking about a permanent manned settlement of any size, not a mass migration.

Basically most people realise it's a marketing scheme to keep the whole Musk God aura going. It's not actually going to happen.

You know Musk didn't invent the idea of Mars colonisation, and isn't its only advocate, right? NASA is also serious about a manned mission to Mars.