"* but good" is the vast majority of successful tech companies. iPhone wasn't the first smartphone. Facebook wasn't the first social network. Google wasn't the first search engine. Etc.

I would assume most of their early customers were not using Plaid exclusively, because they only supported a handful of very big banks. Every company that I've seen select Plaid as a vendor has either done so after considering many alternatives, or used Plaid data alongside data from other providers.