What to learn to build platforms/software we use day-to-day?

I'm inspired by the apps we use daily like Discord, Reddit, Robinhood, etc. and software like Stripe, GitHub, Databricks and so on.

I believe there is general pattern in developing, packaging and shipping softwares (correct me if I'm wrong). What's that pattern?

Can I please have some guidance on what to learn or path to go to build platforms independently (even if it's impractical for one person to build these things).

Any help/advice/roast will be appreciated!