I'm sure there are better options. OTOH... I was at SO for about 9 years, and the system described existed for all of it - predating GraphQL, predating even ElasticSearch. There's stuff built on top of it that was never envisioned when it was created, and stuff that wouldn't have been possible without it.

At this point, moving to something else would likely be a far more costly investment just in terms of requirements analysis than the migration described in the blog post. Would it pay off? Maybe! But for a critical bit of infrastructure, that's something you put an awful lot of careful thought and research into before you venture to do anything... And meanwhile, that infrastructure has to be kept running.