1. We were always able to get a small group of nerd enthusiasts interested in using bitcoin as a payment system, but that never scaled to more than a tiny group. "Normies" were never going to jump on board with that (and that actually includes a lot of loudly self-professed 'bitcoiners' who could never be bothered to actually use the thing).
2. But ... Bitcoin was never a payment network, it was always a monetary network. The 2012-2014 excitement about getting bars to accept it was never the point. So ...
3. Lightning network is the closest thing we have today to what could be a well designed payment network on top of Bitcoin. It's not 100% there yet and there are some deep structural issues related to security (DOS) and privacy (receiver) but it's at least conceivable we'll fix them, and today Lightning works very well (I use it a lot for online and even in person payments). OpenBazaar was way too early for that, but I think they maybe were in the set of people who grossly underestimated how promising it was in the 2017-18 era. The thing is, even if they had gone balls to the wall on LN they were way too early to take advantage; it was realistically 3+ years before mobile software had gotten good enough and reliable enough to use it. Even now, we are not quite at the userbase level for a big p2p trading market to develop, though it's a lot more realistic nowadays.

1. People hate downloading desktop apps and creating great cross platform experiences is hard

First, we should have spent much more time on some kind of web version, or focused solely on mobile. We spent too much time building a complicated, high-maintenance desktop application. It was always clunky and unreliable and never really encapsulated the experience I had envisioned.

2. Price volatility made people hesitant to accept Bitcoin as payment?

We should have also figured out a way to add stablecoin support for the marketplace. That would have created price stability and mitigated the volatility that inhibited people using the e-commerce platform.

3. Everything can't be free

From a business perspective, we never charged users a fee for using the platform, which limited our revenue options and made it hard to operate at a profit or raise additional venture capital.

4. Talk to your users

I think anyone interested in building a new decentralized P2P marketplace needs to think hard about who their end customers are. There’s a massive difference between a customer trying to send hard-to-find medicine across the world undetected to a loved one versus someone wanting to buy an inflatable pool for their kids. We didn’t make that distinction and fell into the trap of trying to out-engineer our problems. Sometimes listening to what your users need is what matters most.