It's not actually that bad. There's a lot of defense, security, and highly proprietary development that happens on isolated networks. You have to put significant effort into IT infrastructure but you'll end up with all your stuff hosted internally and most tools support custom package repo mirrors (linux distros, programming languages/build systems, docker). You'll also probably have a second system with internet access at your desk if not nearby for stackoverflow et al.
Basically the idea is defense in depth. The valuable stuff (design files, schematics, code, documentation) lives in the air gapped network while communications live inside a VPN and detailed technical discussion is often discouraged.
Basically the idea is defense in depth. The valuable stuff (design files, schematics, code, documentation) lives in the air gapped network while communications live inside a VPN and detailed technical discussion is often discouraged.