This. I'm surprised how many people put the ethical ball 100% in the end-user's court given the climate of corporate behavior and policies.
Yes, a buyer and seller are "choosing" to use the platform. No, this does not mean they want to - it is a result of a lack of options/competition since CL is local, TB is niche, and ebay is a dinosaur. Aren't we seeing the same thing in Reverb that we did from ebay monopolizing the online sales platform for so long? Increased fees, declining customer service, less protection for users, more scams, more huge businesses using it and getting perks you mentioned, etc...
I don't understand why so many humans are so willing to apply ethical and moral value judgements to themselves and their peers, without batting an eye at the fact that large companies/corps have no desire to adhere to the same set of rules. In fact, they'll often leverage their scale/power/money to ensure policies don't get in their way and often become more favorable for them. If someone sees my listing on Reverb as well as TB/Ebay/Instagram/Facebook, and they hit me up on the latter platforms, I'm happy to use whatever route I deem safe and cost effective for the two parties doing the negotiating. If
Sweetwater, Guitar Center, and some other sites become major players in the P2P/used gear market in the coming years, that could change my decision as it drives real competition.