While its true that there are open-access journals and conferences without such costs
To publish open access normally costs upwards of $3k USD as well. There’s practically no point in the publishing chain where academics aren’t getting screwed.
Let’s also not forget that you have to review other people’s papers for the journal for free.
Because if no one reviews the articles then anyone could publish junk. In highly technical fields the only people qualified to tell if something is BS science are the experts in the field, so they review and make sure the article has some merit.
That’s not to say the reviewing process is perfect, but it does at least help to filter some amount of bs.