Sustainable practises, especially energy generation are way cheaper than non renewable sources, so why would corporations try to make energy cost more for themselves?

Sadly, that’s not the whole story. I don’t share all of his takes on how to move forward (he’s a tankie, I lean towards anarchism), but Second Thought summarized very well what the weak point in your argument about cost is: https://youtu.be/3gSzzuY1Yw0

this time the main blame is on the government for not putting the environment first and not forcing adverts for unsustainable products to have warnings about their environmental impact. But the government is installed by people (in democracies) and the people clearly don’t care.

Sadly, you’re also wrong here. For the USA it has been shown that the opinion of average citizens on proposals of individual policies has no significant impact on the probability of the policies being implemented. It is only the position of lobbyists that have an impact. Lobbyists also include environmentalist groups, of course, but more often than not corporate lobbyists all take similar stances whereas non-corporate groups are very often single-issue groups who only make themselves heard on relatively few occasions, making them less impactful overall. https://scholar.princeton.edu/sites/default/files/mgilens/files/gilens_and_page_2014_-testing_theories_of_american_politics.doc.pdf

I don’t know of a similar study for EU countries. My guess is that the multi-party systems here work in favor of more voices being heard but also against implementation of new actually useful policies because of the need for compromise and coalitions.

but I rarely hear anyone talking about banning planes.

Then do it, but in your own post.

I mean that literally, it would be good to ban private planes and cut down usage of other airplanes drastically. However using that to discredit people talking about other drivers of climate change is just plain whataboutism and sabotaging the movement.

Politicians take inadequate measures because they do what the population wants to be reelected on the next term.

That’s the only thing you’re getting wrong here, but it’s a very crucial point. Even in the best democracies on earth, political power does not come from the people as a whole, it is not distributed equally. It’s kind of difficult to prove or quantify but this study succeeded for the US: https://scholar.princeton.edu/sites/default/files/mgilens/files/gilens_and_page_2014_-testing_theories_of_american_politics.doc.pdf

They showed that it’s organized groups who actually influence politics. It’s obvious that lobbyists of corporations and industry associations will be among them, but it also includes unions, climate lobby groups, etc. But corporate lobby groups often have similar interests whereas most non-corporate groups only talk about very few issues, making them less visible (the paper suggests that they’ll be impactful if they all speak out in favor of the same things). Furthermore, who is actually part of such groups? It’ll be the well-off people who don’t have to work two or three jobs to survive. Now it’s common knowledge that the US is far from being the best democracy on earth, but I have a feeling that the EU where some of the better democracies are located works very similarly.

Therefore it’s neither correct nor fair or helpful to blame everyone. The elites need to be held accountable, or even better, be abolished.