People have been hacking on this "if" for a while, and I suspect we will break through to the other side eventually, probably by the end of the decade. The problem is really just that cryptocurrencies like monero want to minimize their use of scripting, because transactions with scripts are a heuristic that can be used to de-anonymize you. But payment channels require some sort of timelock, in bitcoin this is done with HTLC script.
There have been a number of proposals, I think the oldest is DLSAG: https://eprint.iacr.org/2019/595.pdf There are other ones based on time-lock puzzles, but those have always been kinda crappy.
It may be possible with some ZK magic I'm unfamiliar with. But the core of the problem is that we need to find a way to make a transaction valid but only after a certain block height, and make it so that validators can't learn any specific heuristics about the transaction (like what the block height is exactly).
>But my point is that even if a magical technical solution existed tomorrow then the same sites that collect data for ads would continue to do so for the much more valuable data on paying users.
Sure, but after the micropayments revolution there will also be a change in the types of sites people use, enabled by the new form of monetization. You could rely more on people posting things like videos to their personal blogs and interlinking them instead of having to shack up with one of the few sites large enough to support ad-funded monetization. The internet would have a basic spam-resistance function, so it would be less reliant on the existing players to gatekeep (for example, email, forum moderators, etc).
I think it would be more competitive. Let's say you have a site like twitter that says "now that there are micropayments, we will charge you 1 cent per pageview AND force you to login and collect your data", well then you will have a competitor like xcancel.com which can charge 2 cents per pageview and not require login. The market would decide what the best model is. Right now proxy sites like xcancel have to do it for free. Even if they wanted to run ads, the ad market isn't competitive in the same sense because it is more profitable for larger players.
I think you mention in your blogpost that no one would want to support micropayments because of piracy. I consider this a massive advantage of the micropayment system. It's pro-piracy by default. If you look at the origins of ad-funded sites like youtube, they started out as hubs of (light) piracy. The content of social media sites should be pirated and mirrored: they are just getting rich off of network effects in the first place. If you combine micropayments with some sort of bittorrent-like system, this could be very powerful. Imagine a decentralized archive site, where you take advantage of TLS to archive a verifiably timestamped version of a page, and anyone else can send you money that is conditional on you providing them a copy of that archive in return.
Micropayments don't fund the development of new intellectual work, but they let you recoup the cost of bandwidth. He who does not host, also does not earn. If you want to fund the development of new work, I think you need patronage. We are already seeing this with a lot of videographers from youtube depending mostly on sites like patreon and donations from dedicated fans. In a micropayments world, you wouldn't have sites like patreon taking a cut. Aside from just having ~0.1c micropayments-per-pageview, you could have very easy p2p "mini-payments" on the order of ~$1 in exchange for donation rewards.
With less money in the annoying ads economy, google and others would have less power to alter the web standards to their whim, and we could claw back features that enable fingerprinting. I don't know, that is just my dream.