Yes, I agree on the ultimate control of your data being an issue. I too have the concern, because let's face it, nothing lasts forever. I've found that the guys over at Athens Research and Logseq are both trying to solve this issue by operating like Roam and Obsidian combined, which is exciting. They are still very much in their development stages and haven't released a way to access it from my phone, which is a big deal to me, so I haven't felt comfortable making the switch yet.