If you're launching an e-commerce site that sells shoes or something, yeah, you probably aren't going to sell a billion shoes every year so MySql is probably fine.

Finally, I use this example a lot: Github thought they could scale out MySql by writing their own Operator system that sharded MySql. They put thousands of engineering hours in it, and they still had global database outages that lost customer data.

You get that shit for free using Scylla/Cassandra (the ability to replicate across data centers and still fine grained control to do things like enforce local quorum to not impact write speed etc.)

They probably made the wrong choice.