Building is about using whatever you got from those activities and mining. And the normal player will not start building a massive base at lvl 1.
But it used to be possible. I myself play mostly looter-shooter nowadays, so I'm not about to ragequit over the changes, but I have enjoyed the couple dwarf-mode playthroughs I've done over the years. I will probably give one a go soonish, but I'm guessing it'll end up requiring an outright two weeks of questloop to get going. And that's kinda against the idea of the whole self-sustaining thing; IMO artificially so.
Just now our group <snip>
Hmm. Not playing MP, I can't really say much, the scaling is weird. Watched an ~8 player group take the week one horde in a cobblestone cube, size of which would be easily done by one player during the first day (at tops two). With no issues, other than the random spawns of 25 cops or demos by the host ...

I'd say two days for a d14 horde is overkill, especially if it's a group effort - but then the group might be, you know, Not building for the most of the time...
I don't disagree in principle, but took me a while to figure out what's the third source. There's no looting without questing in my world, and there's no questing without getting dukes to buy stuff. It is a legit difference, looting vs trader stock, but in SP, I'm spending my dukes just to spend them.. The best stuff comes from quest rewards, low tier lootboxes are nice but usually won't offer significant improvements. The trader inventory occasionally has a game-changing upgrade, but mostly it's electric stuff and books for me; and then a progress skipping chem station.
All of it is basically aiming for T5/T6 quest rewards, preferably ASAP. The cement mixers and crucibles just show up "for free" along the way.
But yeah, practically it looks like the skill magazines are going to end up being the "minimum rate of progression", with trader RNG likely pushing better stuff when lucky. Which makes the magazine system rather meh, they're there, but they're not doing anything 95% of the time.
One upside though, I haven't had to think about spending points in cooking in any of my games yet, the kitchen cook books have given me grilled meat recipe early enough without the point...

For the couple of the sideshow things they seem fine, cooking, seeds. Then again, I wouldn't mind a trader buff where the trader can actually teach you the basics, either from just outright buying it, or specific quests (Jen tells you to get 100 aloe for her supplies and teaches you to make bandoes..).