Earlier quoted context omitted.
If you were refused by Amazon, Microsoft, Google and Cloudflare, what alternatives are there?
10 years ago no one was running in cloud. Internet still works outside of big tech data centers.
Peering ISPs would frequently drop routes + messages from whole data centers that would blatantly ignore spam complaints, which would force their hand to kick the offending customers off their platforms that caused harm to their other non-offending customers.