You need a big team to maintain the platform and provide a controlled access to do stuff (PaaS is the buzzword) and then a bunch of above-average devs that are motivated, trained and incentivized to do their own bits of Infra properly.

Possible at FAANG[1] but gets a lot harder as companies get smaller and/or the devs teams are not setup to do that.

[1] I assume the SREs are not the only ones doing the Infra code