I didn't underestimate anything really, I am supposedly an expert in the field.

I have used 100GB+ workloads on sqlite, its great, its useful, and its still extremely limited compared to the featuresets of other mutli-user relational databases.

Oh, and the "and he doesn't even use joins" doesn't really show that sqlite is great at anything, its materially more difficult for a query planner when joins come into play, its the normalization and deduplication benefits (which can play into performance benefits at certain scales) that make a join useful.