Ex-Googler here and 20+ year veteran of SF startups.
It sounds like you have a great set of intuitions, and you're right, all that infrastructure is a nightmare to set up and manage.
Step 1: Question every requirement
Step 2: Drop everything that is not critical
Step 3: Profit!
Git hooks and Makefiles are great!
I have an HP workstation I bought from eBay under my desk that has 32GB of RAM, 2x 12 core CPUs and a static IP address. It's probably 8 years old, but fast enough to serve whatever we need for a long while.
The machine (Old Blue), hosts our Git repos, web app, database and integration service (git hook that calls, 'make publish').
We're not serving Google scale traffic, so we don't need Google scale infrastructure.
Keep it simple whenever possible and don't let the modern stack complexity creep in until you absolutely need it.
Even going to the cloud, when you've done it 10 times and know how, is way more work than you need when just starting out.
Take on those costs and complexities only when your traffic requires it, and you may just find out that you never have to pay rent for compute.