Let me guess, the walls seemed "paper thin"? That is very easily fixed by basic sound proofing and insulating shared walls. Or by using brick or concrete. I lived in an apartment with 3 other guys that had brick walls and I could scarcely hear anyone. It was amazing.
There are tons of poorly built detached houses as well, that are also not easily or cheaply fixed, that is orthogonal to the debate between house or apartment.
If you live in a high quality house with large space between houses, maybe. Sound is very transmittable by air, if you are in the garden or open a windows there goes the sound insulation. There are tons of houses with 'special cardboard' as walls and not really that much distance laterally between the houses, so all the loud sounds will be heard. Again, if you build with bad quality, anything will be bad.
sweden has a lot of "commie blocks" built around the 60's, which are generally basically solid concrete, and straight up the only time i hear my neighbours is if they drop heavy stuff directly onto the floor or if we both have a window open.
These buildings were made specifically to be cheap housing, and yet they seem to be some of the better housing available in the world, fucking wild. I maintain that our commie block areas are some of the best places to live within the country, you get hilariously cheap rent, car-light surroundings, generally very decent public transport connections, and it's not unusual for them to effectively be the situation depicted in OP's image, some example areas being Bergsjön, Fisksätra, and Jonsered, the latter of which is wonderful because it's effectively a small town consisting solely of apartment buildings.
The holes in your logic are the individualism and scale. Very few people will ever be able to live in a detached house like yours, by definition. Either the forest will eventually be cut (rendering the nature dead), or the supply will forever be small and expensive (not accessible to millions of masses). The only way millions of people could have access to a large natural area to hike is indeed apartment blocks urban islands surrounded by large spaces of nature, like the 2nd image. They don't have to have tens of floors, just 5 floors of large apartments can house many people with comfort while also having amenities (that can be paid sustainably too) to boost.
Bullshit. Once you've built your giant rabbit hutches for human, you're going to need all the accompanying services these giant misery factories need. Industrial scale services for industrial scale human storage facilities.
Go live in one of you want to, share that one sad looking tree in your one sad looking park where you're not allowed to walk on the grass with ten thousands of other people.
Don't forget your antidepressants and your sleeping pills.
Fine suburbanite, everything that is not a private garden will automatically suck for you, and apparently there is not a single dirty ugly and bad backyard, garden or house itself wherever you live. Here in Brazil, tons of people leave mosquitoes proliferating in suburban houses, turning them into vectors for dengue, chicungunha, zika, etc. Can i say every suburban house is a cesspool too ? are all these Moscow parks , Tokyo parks full of dog shit and druggies all the time too ?