Check the given definition for start-up. A start-up doesn't have $200+/month for managed Kubernetes, cloud storage, cloud CI/CD pipelines, CDNs and all the other niceties. Also, not all start-ups are born in Silicon Valley or nearby, nevertheless 90% of all start-ups fail, some of them because they waste money on cloud infrastructure while hallucinating time to market tomorrow and are unable to be lean, duct taping and WD-40-ing (soon ChatGPT-ing) some disposable infrastructure for pennies.
I can guarantee you that they are wasting more than 200/month of an engineers time and mental energy to manage the bare metal setup vs the cloud managed offering. Its penny wise and pound foolish.
I am a one-man start-up, well, trying to be for some years now, and I run a similar bare metal setup as the one above. Haven't touched it in 142 days and it costs next to nothing vs. the $200/month that I couldn't afford even if I wanted.
Again, maybe the word 'start-up' has too many meanings. Sure, once you have 1,000+ paying clients you will be able and even you will need to rely on cloud infrastructure, but 90+% of start-ups never reach 1,000+ paying clients. And again, it's not that complicated, pretty much everything is a Helm chart, and when you are merely trying things out, not even close to product-market fit or monthly recurring revenues, you can afford to have the cluster down for days on end: there is no one to care.
These are all industry-standard tools that you could also run outside k8s in docker-compose, I fail to see anything bespoke here.
If your team cant recognize some of the most common proxy, s3 storage, database, operating system, cron job, backups, load balancing tools from a few feet away or manage a server then you have a problem with vetting candidates.