Best case scenario is that I don’t exist in eyes of big corps.

Actually best case scenario is that they just lump you in with other people who try to get privacy or block ads, because it's such a miniscule number of people who do it, it's actually more likely that they can profile you based on your habits of trying to regain privacy.

It's a vicious cycle, the more you do to try to make yourself anonymous, the more you're actually just putting yourself in corporations "privacy conscious consumers" box and they're just waiting for the right products to shill at you. ("I feel like I'm caught in a web!")

It's actually part of the reason you see more "privacy respecting services" popping up, with lots of questions about how much they actually respect privacy. Privacy, like everything else, is now a product to be sold.

Also, you don't actually want to not exist in the eyes of big corps. If you're stuck using one of their services and you've been memory-holed in some way, getting help to solve your issue (your Google account being banned for no reason, your Uber Driver account never given any riders to pick up, and so on.) is nearly fucking impossible. These companies don't have human customer service anymore, and trying to climb out of a "digital black hole" is a fucking Kafkaesque nightmare.

For me, privacy in digital world is pratical of self awareness. You do everything cautiously (means constant effort like you said), aware and take care about all technique and information gathering about us from big corps to not let them run free unconsciously in our mind, have self esteem to control what we can control so we're not overboarded by information overload, regain ourselves as full human beings with reason "there's a thing I need to hide" that keep us sanity hygiene, and deep thought about every platform we used + calculate the impact from that.

Everything what we carefully plan will not according to that in digital or real world forever, and that's how this world works. But as an individual and human beings, we have a choice on what we stand for. The word "Privacy" for me is just a pop culture in digital world after whistleblowers become trend (Julian Assange and Edward Snowden case for example). But essentially, "Privacy" is our human rights and "self defense mechanism" as a total individual to stand for our rights when some group with scale of power using that position only for their own good rather than for the good of masses.

There's a distinction between "for own good and for the good of masses" that basically return on how we perceives our own needs to not over-have something that only can controlled by self awareness and self control according from life experience and the knowledge we have. By means, regain our privacy is to regain our human rights.