I've taken showers with hot water, showers without hot water, baths with and without hot water, I've washed myself in rivers, lakes and oceans.
You really don't want to give up your hot showers/baths
Especially if you don't live in a really warm climate. You get used to it, but let me put it this way: a hot shower/bath after going without one for months or years is better than sex.
At least it was for me.
Cavemen would have taken hot showers if they could have. Wild foxes would sleep in beds if they could.
Comfort is not a bad thing, but you're on to something: too much comfort can be.
There is so much value in spending a lot of time outside, picking and gathering your own food. It helps keep you connected to the world around you, the life around you.
You can go forward without going backwards. Cavemen didn't know about electricity or supermarkets. You know and want to
mindfully give up some of those things. That's different from going back to being a caveman, that's going forward!
Try not to worry about what other people might/could do. This is your path, follow it if it feels right
One more thing: I stopped eating processed food (except for soy milk and sweetener for my coffee, eventually I think I'll switch to raw sugar or something) and modern grains just recently but I already feel so much better. Diet is an incredibly huge part of your well-being. Change your diet to fit your current thoughts and see what happens.
I also stopped eating meat. I wasn't eating much meat to begin with, maybe once a month, eggs I sometimes ate a couple of times a month, so that wasn't really a huge change. I just personally feel better now, not eating animal products. Might not work for everyone.
I'll entertain your last question. Yes, people will stop experiencing outdoors/nature more and more. Eventually there will be domes around cities with no naturally occurring animals or trees inside. Even later, it's likely this planet will be surrounded by an array of microsatellites armed with various energy weapons to scan and, when needed, destroy any particle, organic or inorganic, making this planet a closed system (a gated community, if you prefer). At that point, the amount and type of life on this planet could entirely be decided by humans from creating new species to eradicating every last one of existing ones and eating nothing but 3d printed artificial food.
Scary thought? That brings me back to my suggestion: Try not to worry about what other people might/could do. This is your path, follow it if it feels right
O Immortal, O Soma
Pavamana, Word of God
In flesh and living blood
Resurrected fruit of the Tree of life