Sure, it's true at some point that the Platform could, for whatever reason, decide it would rather suck you dry than continue the symbiotic relationship, that does happen.
But here's the core of the problem - by putting yourself half out of the platform, trying to direct people off to your own website, by gating your content etc. You are damaging the platform. All that massive surplus that is created by having everyone in one place sharing in one common way? It won't exist if you're not participating in it.
I can open a shop in the centre of london. I'm going to pay high rents, but I'm also going to gain massive benefits from all the people in London who can come and buy stuff from my shop. It's a win for everyone. You're going to open a shop in the centre of London and when someone walks in the front door you're going to say "Oh well here's all the stuff I sell, but to actually buy it you need to come visit my farm in Norfolk". You see how this doesn't make sense right?
And laying aside whether you should do this, any platform that wants to survive is going to massively penalize your behaviour because you're freeloading, you're damaging the platform. You want surplus but you don't want to let anyone else benefit.