At larger orgs who already have a functional business, yes. Running a 0-1 startup is different. There's barely enough time for senior engineers (usually founders) to build core infrastructure and product - let alone document, onboard, and mentor junior devs.

Agencies and consultancies the best places to learn as a junior IC. Reviews, process, and management are built in and there's a ton of variety. You also get opportunities to try a bunch of different hats before deciding where to specialize.