I don't think that's realistic. Harry's acknowledged that he needs to mature into a worthwhile adult in order to be able to save the world, and he's not going to gain the experiences he needs to do that (or indeed maintain a reasonable standard of mental health) by becoming a full-on hikikomori.

There are better ways to keep yourself safe than invisibility,

Not many, especially for someone too young to have the raw magic for most powerful spells. When it comes to protection, having no one know you're there is the next best thing to not being there.

Additionally, Harry's first instinct when he realised how much personal danger he was in was to wear the Cloak 24/7. It seems odd that this instinct is 100% absent now that his survival also represents the survival of the entire world.

It was Hermione who knew more than than Draco and Harry how to properly make use of her army.

In fairness, it was Quirrell who gave her the idea. She was flailing until he spoke to her and then assigned a deliberately chosen group of people to be her army.

Draco was confused.

Therefore, something he believed was fiction.

Granger should not have been able to do all that.

Therefore, she probably hadn’t.

I promise not to help General Granger in any way that the two of you don’t know about.

With sudden horrified realization, Draco swept papers out of the way, hunting through the mess on his desk, until he found it.

And there it was.

Right in the list of people and equipment assigned to each of the three armies.

Curse Professor Quirrell!

Draco had read it and he still hadn’t seen it—

-

It was Hermione who formed and led a band of Mighty Heroes.

It was Hermione who inadvertently gave a bunch of 12-year old girls the idea that they should rush headlong into danger against superior opponents, and then was forced to stick with them as damage control.

“Huh,” Lavender said, now looking thoughtful herself. “That’s true. We should do something heroic. I mean heroinic.”

“Um—” said Hannah, which very much expressed Hermione’s own feelings on the subject.

“Well,” said Parvati, “has everyone already been through Dumbledore’s third-floor forbidden corridor? I mean everyone in Gryffindor’s been through it by now—”

“Hold on!” Hermione said desperately. “I don’t want you doing anything dangerous!”

There was a pause while everyone looked at Hermione, who was suddenly realizing, much too late, why Dumbledore hadn’t wanted anyone else to be a hero.

Most people simply didn't have the power to combat Voldemort. Doing what you can isn't getting yourself killed trying to do what you can't.

There are plenty of things they could have done to support the war effort without fighting directly. Economic support, for example, which it seems from Dumbledore's Pensieve memory was limited to a few wealthy families.

Let's not forget this:

But I knew the Muggles would eventually destroy the world or make war on wizardkind or both, and something had to be done if I was not to wander a dead or dull world through my eternity. Having attained immortality I needed a new ambition to occupy my decades, and to prevent the Muggles from ruining everything seemed a goal of acceptable scope and difficulty.

If you can come up with a plausible reason why Dumbledore would pretend to be Deathist, I would love to hear it.

"...so shall it be," Harry repeated, and he knew in that moment that the content of the Vow was no longer something he could decide whether or not to do, it was simply the way in which his body and mind would move. It was not a vow he could break even by sacrificing his life in the process. Like water flowing downhill or a calculator summing numbers, it was just a thing-Harry-Potter-would-do.

I think gattsuru is referring to global immortality, as Dumbledore is a Deathist.