People boycotting certain products only really works if an alternative is available and attainable, or the demand is elastic.

For example, if I go to any grocery store, all the pasta, rice, buckwheat, bread and other staples are packaged into single-use plastic, as are hygiene products like toothpaste and shampoo. I have no choice but to be part of the plastic waste problem since there is no alternative and the demand for food is not elastic—I literally can't go without food and basic hygiene.

But I can and will avoid buying problematic products like teflon cookware, fast fashion, ICE vehicles, tech products with severe privacy/ownership/repairability issues since there are alternatives available and if not, I can go without since eg Alexa smart speakers are not essential for life.

Hence, we need to hold companies, whose products are problematic while not having alternatives and that are essential for life, responsible and force them to change to less problematic practices. In short, eg single-use plastics should be regulated out of existence wherever possible.

And for products that have better alternatives, we need to raise awareness about them and raise their social acceptance/desirability (make them cool). Plus we need to increase their availability and attainability—what use of is an ethical alternative product if it's not easily available in my country or if the price is not affordable to everyone who can afford the "normal" version?

Indeed

Claiming that oil companies are to blame for producing all that oil seems stupid. If you use less oil, they make less oil

That's not really what OP is saying though? They're talking about corporate efforts to make it seems like the consumers are the problem, not them, and many are still falling for it. As long as the awareness of this is not raised and more people aren't pointing fingers at the corporates the whole don't buy their product is never going to be effective, same for advocating for regulations (rather, especially the regulations). You're assuming everyone knows the root of the problem already, but that's just not the case here.

I think the point is not that the individual should abandon efforts to modify their own habits. The point is that we should also be focusing just as much if not more energy on efforts to regulate and/or change industries that are responsible for more emissions by orders of magnitude. Some small but significant subset of the population going vegan, buying electric cars, or biking to work isn't going to offset the biggest offenders.

The biggest offenders are fighting tooth and nail to be as profitable as possible at literally any cost. You can be damn sure that if what they produce becomes less desirable in one industry, they will try their hardest to get picked up in some other industry. They'll have scientists finding some way to be useful somewhere and demonstrating it with research and lobbyists that will then get the government to mandate/subsidize it so that they make as much money as possible.

I've personally tried to "vote with my wallet" but industries have found ways to green-wash their products to give the impression that choosing their products would be the responsible choice when in reality it is not. Ensuring that your spending only goes to companies making an honest effort to do all they can to be carbon neutral or environmentally friendly is more than a full time job at this point. The only way is to ensure that governing bodies dictate the behavior of these organizations and even individuals so that it is no longer up to the organization/individual to "do the right thing".

Without proactive, strong government intervention we will be well, well, well beyond the point of no return by the time "voting with our wallets" and "modifying our behaviors" changes industries and society enough to have a significant impact.

This is a frustrating kind of defeatist attitiude I'm finding is getting more and more common.

It comes from a place of unwillingness for personal and habitual change. It's hard to accept that we all have to change our lifestyles and accept that how we're living is going to have to change. That there is exists some scenario whereby we all continue living exactly how we're doing now with the same consumer behaviour and expect a bit of regulations to change everything. Or delay changing until after these regulations are in place, when in reality BOTH needs to happen.

What's the point in sitting on your ass complaining about the behaviours of other individuals and organisations when the only thing you have direct control over is your life.