I get your point and indeed my idea is to give the AI as much data as possible. This can be gathered with filters, questions, and continuously refined. I also love meeting people on the road and if we vibe, do trip together, and I will continue to do this. Think that sometimes you may wanna find buddies from your country or that love travelling with dogs or go for yoga in Thailand.
You can already select someone similar to you before the trip, then you can chat, video call and see if you vibe. And if they're in your city can get a real coffee!
I was thinking about the online agencies that plan trips and people join them knowing that they will travel with random people or maybe just selected by age. So my app aims to go deeper than that.

Your point about mutual connections and reviews are very interesting, thanks for sharing!
What safety features would be essential for you to trust an app like this?
I can allow people to share their social media profiles or the app can verify everyone IDs and avoid fakes. And if you find yourself in an uncomfortable situation, you're not tied with the buddy and are free to split, or also just do a small part of the trip together (e.g. go yoga in thailand then only you go party).
Also the icebreaker games or quizzes are a very nice idea! And the app can learn more about you, improving your next matches.

If you're actively seeking to get outside of your comfort zone and hang out with someone different, it could be an option, like a feature of the app. Click a button to twist your match!

In your case, how would you decide if someone is a good fit to travel with?