"As soon as your infrastructure becomes more complicated, you can use Heroku instead of hiring people to manage it for a while"
Having a Iaas/Paas doesn't mean you don't have to manage anything - that's a myth. Sure, it might be doable if you own a trivial app with just 1 web server + 1 app server + 1 database server. But once you're doing anything remotely complex like building a 10-node Elasticsearch cluster that is running out of RAM, or a 10 Cassanda node cluster, or a Kafka queue that can overfill, you always need an engineer to manage your infrastructure.
Wouldn't call that true. There are hosted solutions for ES, Cass, and AWS has kafka alternatives. That's not to say no enginenering time will be spent, but certainly you can start without a full time infrastructure guy
Yes, you can start, but once your app matures and you rely on it for production, you definitely need an engineer that you can rely on if things blow up.
I know companies that don't rely on any hosted cloud services for our infrastructure, and have just 1-2 people they rely on to be that infrastructure guy, and even they are not 100% full-time. It's only when things blow up that they tell him to stop what he's currently doing, and address the issues. Unless you have 10K+ employees, you'll be hard pressed to find companies that have full-time engineers that just twiddle their thumbs, and stare at a monitoring dashboard 40 hours a week to monitor a component.
Having a Iaas/Paas doesn't mean you don't have to manage anything - that's a myth. Sure, it might be doable if you own a trivial app with just 1 web server + 1 app server + 1 database server. But once you're doing anything remotely complex like building a 10-node Elasticsearch cluster that is running out of RAM, or a 10 Cassanda node cluster, or a Kafka queue that can overfill, you always need an engineer to manage your infrastructure.