And how many people are going to involve some third parties instead of just tossing the item and buying a new one?

The problem is to think of a market structure where third parties are involved:

Current EU-system, the seller is always first point of contact in case of defects. So the seller should involve a third party and then share costs (after 5, 10, 12 years depending on reasonable durability). So the market for third party repair isn't a consumer market!

The only products I know third party repairs exists are: cars and household appliances. And even for household appliances the above holds, much goes via the seller. That it doesn't hold for cars is, I imagine, mostly lobbying. Even there collective consumer action is on the rise.

Then there is an additional problem: technical progress. Having recently replaced many household appliances (mid-30s now, so everything was 10yrs+ old), my machines use 30-40% less energy (from A to A+++). I'd be an economic fool to keep the old machines. Law requires the supplier to take care of the waste, so I really have no incentive to keep the old machine in use.

I'm a big proponent of 'right to repair'-rules BTW, but think they do not add much to the bigger picture. Pricing of household appliances as a function of the running costs have fallen dramatically. So repairing just makes little economic sense. The environmental impact, I'm not sure. I guess 100 kg of waste is a lot more damaging than a few thousand KWhs. But that all depends on the way disposed machines are treated. Cradle-to-cradle could make a lot bigger impact than right-to-repair imho.

Depends on the price of an item relative to one's wealth. I pulled the book on a seller just once in my life - I had a shitty job, and I saved up for an expensive tablet, only to get one that was broken and have the seller (a big brand in my country) try to weasel out of replacing it. It took a strongly worded letter to company's HQ to finally get them to replace the product, and while I was ultimately successful, the whole experience was pretty mentally taxing. I'd say taxing enough that it's not worth it if the item costs less than 10% of your monthly income.

However, I do know of people who fight for their rights as consumers as a matter of principle, and I actually applaud them. They do a good work for the commons.

I've had similar experiences with electronic shops. One thing that's really helped me is legal counsel insurance. It's about €5,- a month for the entire household and if a shop doesn't offer a fair solution, I just give the insurer a call and they take care of everything. It's saved me a lot of time and headaches.

Didn't even know that such a thing exists. Thanks!

More than zero. Beyond that, it doesn't matter because it's not relevant.

Of course it's relevant. If enough people don't bother with getting their stuff repaired the increased warranty has no meaning. It's cheaper for the manufacturer to keep producing crappy stuff and fix it for the small number of people who care about their rights than to increase the quality (and the price) of their products. The waste problem remains.