For the record I did not downvote.
But I capitulate on your point. It would be great if every piece of software was written with resilience and uptime in mind.
As a former sysadmin that sounds like a dream. But I don’t think I have ever seen that with any mainstream program that I’ve had responsibility for. Does that mean all those programs were bad? I don’t think so. We wouldn’t need sysadmins if all programs were written the way you describe.
Programs can be written to auto rotate their logs, compact and reindex their db’s. Using browser updates as an example, they can even safely auto update and revert back on failure.
How many programs actually do these things? My experience is next to 0. But I wouldn’t call them all bad or poorly written programs.
You can have it all with one brokerage in one fund and still be diversified. Suggest reading up on the 3 fund portfolio or boggle head.
S&P 500 is top 500 US companies. Many folks consider that diverse. You can also probably find a US Total Market fund. That will be even more diverse as it will include small and mid size companies in addition to the top 500.
Alternatively, even more diverse would be a Total Market fund. These typically include international companies, and represent the biggest diversification you can get.
No need to worry about Vanguard versus Schwab . The underlying stocks of the fund is what matters.