While it's true that this is a populist talking point, some minor quibbles:

• In 2011, nuclear produced around 18% of German electricity. In 2022, that had decreased to 6% as Germany had been shutting off a few reactors each year. Essentially you're right though, Germany never rivaled France's 70% nuclear figure and if nuclear were supposed to have a future, Germany would have needed a lot of new reactors and that would have been cost-prohibitive.
• Canada proves that you can extend the lifespan, given significant investment.
• With nuclear, a lot of the money is spent upfront. By the time you make that calculation, the biggest chunk of the money is gone, as long as you don't build new reactors or perform massive do-overs like Canada did. Thus discussing the economics of already-built nuclear reactors is a bit pointless, unless you're purely doing it to learn from your mistakes (i.e. prevent building new reactors).