Was the subsidy system which was in effect in 2010's unsustainable? I think so, yeah. But the changed policies resulted in companies producing solar going bust, and the Chinese firms, which were doing fine, were able to buy out the patents and know how.
So, did Germany waste billions? Yes, but by letting the solar producers go bust.
These "they" are different Bavarian persons and groups depending on topic, but the net effect is that Bavaria is Germany's energy bully.
Fortunately, several gigawatt-class HVDC lines are coming online this year. These somehow happened despite the protests, it's a minor miracle.
Sweden's electricity is ~40% hydro, ~27% nuclear and ~23% wind. How is this in any way comparable to Northern Germany?
-- which has 4 bidding zones.
Sweden has lots of potential for long-term energy storage as hydro power, which makes wind power viable. Northern Germany is mostly flat and there's not even close to enough storage capacity (on the order of ~weeks) to make a wind powered grid economically competitive.
There has been a long standing request to split Germany into multiple price zones[1], because Germany as a single zone does not adequately match the underlying network transmission limitations and there have been multiple occasions where power flowed through neighboring zones, which in turn required both network upgrades[2] in the zones neighboring Germany and expensive redispatch[3] in the south Germany. Industry in the south of Germany fights this back as this would mean the energy prices in the south would rise (and drop in the north), as when the transmission lines are congested, the prices start to diverge.
Keeping Germany a single zone is essentially a subsidy to Bavarian industry. The industry fights this so hard that it has basically become an energy insider joke.
[1] https://www.cleanenergywire.org/news/grid-operators-recommen...
[2] https://www.pse.pl/web/pse-eng/news/news/-/asset_publisher/6...
[3] https://www.ffe.de/en/projects/potential-for-reducing-redisp...
That's because China itself is mostly coal, not because of anything magical about particular sources. However, coal is now in decline even in China: https://ourworldindata.org/profile/energy/china
Before someone (accurately!) says the decline in coal is tiny and one year doesn't make a trend: This is likely to continue until there is no more coal for the same reason the UK also completely stopped generating electricity from coal: cost.
PV's absurdly cheap. China has a lot of land, doesn't need to care about optimal use of the Gobi desert.
The 39C3 video "Recharge your batteries with us" is an emotional call to action "We Can Do It!" solar panels everywhere, without showing the other backbone of the German electric grid: the German gas and coal power plants.
I would recommend other CCC video:
"Deaths per TWh" The Price of Energy and Reducing CO2 Emissions
You have to have a backup, the devastating effects of week long electric blackout in winter in a future Germany heating homes with heat pumps, would be comparable with a major war.
Will there by push, after the new gas power plants will be build, to use them not only as backup, but as gas peakers? Probably yes, but this dependents on future CO2 emission costs and natural gas costs.
Even the previous government was planing expansions of gas power plants.
https://www.ingenieur.de/technik/fachbereiche/energie/12-gw-...
Personally, I think Germany should have not exit nuclear energy production but expand it, but this error was made in 2000s and Germany has to live with the consequences.