You can't install them at once, as result at any point in time you'll still need to buy to cover increased demand or replace old units

Huh? What prevents you from installing them "all at once"? The downside is obviously a long stretch of no sun, and for Europe winter being both low solar production and high energy demand due to heating which the soon-to-be-cheap grid scale batteries don’t really fix. The logistics of PV don’t seem difficult though - it seems by far the easiest of the power generation methods, even if the synchronization can get a bit tricky in a large grid.

Because manufacturing isn't there to do everything at once. You install say 50gw per year, each year. In 30y you need to replace first 50gw batch and so on

Any real system will also have backups and emergency reserves.

Lean more on them as you solve the supply chain issue.

No need to make a mountain out of a molehill.

Solar panel materials are extremely toxic (current tech), or are toxic unless properly processed (hopefully, but likely, future tech).

So they won't be made in the EU, since nobody wants to make concessions here. Solar panels have the same problem as oil and mining: they will destroy nature somewhere, otherwise it doesn't work.

They don't have the same problem. They have approximately one tenth of the problem until reprocessing reduces that even further.

Which materials do you mean?

https://blog.ucs.org/charlie-hoffs/how-are-solar-panels-made...

Crystalline silicon solar panels have about 95% market share, and "By weight, the typical crystalline silicon solar panel is made of about 76% glass, 10% plastic polymer, 8% aluminum, 5% silicon, 1% copper, and less than 0.1% silver and other metals."

Everything that is manufactured is made out of atoms, and you can say that any manufacturing requires some nature destruction in the aggregate. But solar electricity requires far less mining and natural despoilation than fossil-fueled electricity.

Solar panels contain quite a bit of lead, and small amounts of cadmium. Lead can be taken out if you're willing to pay a bit more, in other words it never is. Cadmium is required. Other metals are sometimes present.

So solar panels are classified as hazardous waste.

Cadmium is only required in cadmium telluride solar panels, which have less than 5% global market share. Lead solder is still common in crystalline silicon panels, though not universal; modules built with heterojunction cells typically avoid solder because the cells can't tolerate temperatures that high:

https://onlinelibrary.wiley.com/doi/full/10.1002/pip.3688