I've seen some miners or entities approach 51%. They need much more than 51%.. or 50% + 1. It has to be sustained too. I'm not talking about PoS, we are talking about miners, proof of stake was never in the discussion. I'm not confused.

I've yet to see any miner or group of miners or government even attempt to try to do 51% (or more, as needed). You say it's so easy, but why haven't they done it? There's also a lot of bureaucracy involved.

As for vendors, if they just wait 10 seconds after they first see the transaction and then check the transaction in question, they can determine if a double spend is likely or not. Part of that would be to not immediately accept if RBF was used.

That video is mostly false propaganda, but I stopped watching after about 20 seconds when they started using the usual "bad" words to describe bitcoin. Waste of time to watch the rest of it. The first few comments says a lot already.