Your points are valid, but that doesn't mean we should do nothing. Enforcing federation and using copyleft licensing are both strong defenses against centralization and network dominance by a well funded third party.

As far as GPL goes, from what I've seen, big tech companies tend to take it pretty seriously. There is no reason we shouldn't be using that, and other license protections if we have the option.

As for natural centralization over time, I think that is a far less urgent problem than the current risks we are facing, those being major network fragmentation due to the use of defederation, and the risk of centralization around a proprietary platform and/or instance.

Removal of defederation and strong copyleft licensing seem to be natural first steps in combatting that risk.