We do want to speak to folks building new applications as Tigris takes away the infrastructure burden completely from the start. We want to bring the same API experience to "data" as you get when using Stripe API for financial transactions.
Migration is often times necessary. In my experience I have seen countless examples of migrations once an application becomes popular and the backend technology choices at that point either become brittle (hard to keep adding new app features), or do not scale. So I wouldn't categorize it as marginal maintenance cost.
The video, I agree could be improved. Because the pain is not just seen at the maintenance stage, it is felt at every step that you add a new technology to you stack.
Regarding your other comment about "people will go with whatever the default tool". It is actually the opposite, if you give people the choice they will stick to far fewer technologies :) This is why when you see someone building a top Postgres, as an example, initially they use it for the OLTP workloads, then they use it for the full-text search use cases (knowing fully well there is a better alternative because PG is not a search engine), or use it for analytics (even though there are other special-purpose analytical products), or use it for modeling event stream (even though again there is a special-purpose product available for event streaming). This is how application architectures organically grow, and the reason this happens is exactly because it is much easier (development time-wise and maintenance-wise) for me to continue to use X until it is unsustainable. And this is where we are coming from. We want to be that general purpose solution that you can continue to use to build up your application and it will grow/evolve with you.
We did prepare this use-case video, I am curious to hear your thoughts: https://youtu.be/G489hasvgio