Would you consider adblockers theft?

On the flip side, I consider ADs to be theft - especially when there is anything other than truly unlimited data as the only available option:

Imagine you are paying for a plan you can afford, but its rate limitied/set to a certain amount of data - what portion of that data allotment is consumed by ads and ad overhead on every single site you visit.

So the data bucket gets consumed, but say ~40% of that data consumption is actually content you are seeking to enjoy/read/consume

so 60% of your bill is also effectively going to pay advertisers to see their ads on your devices.

So its either a tax on the viewer, or it theft, or its both...

No. I consider ads theft as they steal my bandwidth and computer resources. Ad blockers are theft deterrents imho.