Networks fail people all the time. Mine failed me because I was at one company for a decade(switching teams), and my entire network still works there. I don’t want to go back, so I essentially have no network.
We hired an architect who’s entire network was still at IBM, similar to me. There’s other possible failure modes, it happens quite a bit IME.
Also it's worth noting that while your whole network might be at IBM still, I've found leveraging "I know X, who knows Y, who works at / worked at [target company i want to apply to]". They'll usually only be able to give you a "someone I know but haven't worked with" referral (some places call them just a "candidate lead"), but often it's still miles better than putting your resume in the website intake form. Going 2 degrees out in your network graph is almost always a shockingly large number of people / places.
Almost all the engineers I know get their jobs through random process. They use things like Hired, sending out resumes, responding to recruiters, rooftop slushie (no longer available), and then some actual referrals if they know someone. You use everything available cause you need to get multiple competing offers. You're not going to just interview at one or two friend's places and then get an offer and take it. You're gonna get 5-7 offers and then try to take the best one out of those by making them compete for one another.
This - turns out - requires a lot of companies and interviews and a lot of work.