This is a good question, although personally I don’t like to use a word like convince, as it always sounds like there is an involuntary aspect to it.
What I’ve noticed is that people tend to have a few specific things they’re unsure about. If you can find out what those are, that would help, as it narrows down the problem significantly.
This might be something to ask: what exactly qualifies a framework as a big boy framework? Is it the level of use? Scale of deployment? Number of products sold using it? Companies using it? Specific development processes or standards used? Having gone through specific types of audits or certification? Etc.
It’s easier to answer concrete questions and dealing with facts than sentiments, as the latter are really difficult to change.
Additionally, I’ve also found that – but this may be due to the audience I typically talk to – talking about actual concrete results and showing videos about them helps.
So instead of talking about how things could be with ROS (1 or 2, doesn’t matter), show what they actually already are. This changes the perspective from some potentially idealised picture to concrete, verifiable facts.
Bonus points if you can discuss use- and edge-cases coming from the domain your audience has experience with/in. They should be able to relate to those, and the solutions chosen, much more than say a TB2 driving around the bedroom of a PhD student.
Finally: be honest. As was discussed in ROS2 Default Behavior (Wifi), things are not perfect, fault free or TRL9 everywhere but that’s ok. Any engineer should be able to understand that technology is never completely as it seems on the outside, or made out to be in videos (n==1 of course). The important thing is it’s being recognised and worked on, and in the meantime not marketed as a perfect solution.
However, even with things being as they are, there may still be sufficient ROI or advantage for someone (or multiple someones) to start using it, simply because it would seem not using it would be more costly.