The smart thing to do is NOT get kicked off those large platforms and once you do, it's either extremely difficult or impossible to get back on again. So it's always the safe play to ensure you understand their policies and do NOT flaunt them because you have to remember that you are of no importancfe to them whatsoever.
Their number one concern is their own brand protection, that is what makes them money. They see people who flaunt their policies as a threat to their own brand and is why they deal so harshly with what might seem to be petty small stuff.
In regards to implementing the same policies as eBay/Amazon on other sites, including your own. You should always be fully aware of the policies of whatever site you are selling on. Selling products on websites is essentially the same as leasing floor space in a mall. You lease shop space, you'll have clauses in your lease that you have to follow, and that is what website policies are in the online world.
In regards to selling on your own site, well that's the same as you building your own shop. You're now the owner, you're not leasing from anyone else, so now you make the rules.
In regards to being in the game without the big platforms, well this is the really hard part. People pay extreme rental prices to get floor space in large shopping centres because of the traffic exposure it provides them. They pay that rent because it's not just about selling stuff to customers specifically shopping with them, it's also about attracting customers from the thousands that walk past their store on their way to buy something else.
Eberytime someone new walks past, you're marketing your store to them just by being there!
It always comes down to marketing, so if you don't have rental space in a large shopping mall to draw traffic from, you have to find alternatives to do the same eact job and that comes down to how big is your online marketing budget.
Everyone is always looking for the cheap, effective online marketing option and sure, there are some cheaper options out there, but in reality if you want to create maximum exposure to draw traffic, you have to spend cash and still ensure that you are spending it in the right places.
The best way in my opinion is to NOT get kicked off those big platforms because they can be used as marketing tools to generate you long term business for your own website. Once you burn those avenues, you've just burnt the most cost effective for of marketing for your own website that you will ever have!