Reducing usage of technology can increase emissions through secondary factors. It's a major inconvenience with a minor or even sometimes negative gain (real life activities like driving are more co2 intensive).

Reducing meat consumption doesn't increase emissions because animals already have to eat plants and they already fart on our behalf. If you cut out the middleman (the animal) you need less plants and also fart less. It's a major inconvenience with a major gain.

You can make systemic changes to reduce the amount of animal products that people consume.

For a start, you could stop subsidizing them. For the long term you could fund a massive meat replacement research project.

(Though I disagree with the OP that this is the biggest issue, it is a large enough issue that it's worth tackling it, and certainly larger than streaming video.)

Agreed. Especially since the actual biggest individual contributor (for people living in the developed world) is having children, and we really don't want this kind of individual focus to land there.

My pessimism tends to agree with you.

OTOH social distancing and wearing masks has shown recently that (most) people are fine with changing their behavior, if necessary.

The parameters matter a lot though. With social distancing/mask wearing there is a very measurable risk that's immediate to you and the people around you. With climate change your actions make a tiny tiny impact that's spread disproportionately over the entire planet and takes effect over decades - this makes it much easier to ignore.

If people could get infected with climate-change disease and x% of them die, there would be a lot more action to prevent it.