I work at a small / medium company with about ~20 dedicated servers and ~30 cloud servers at Hetzner. Outages have happened, but we were lucky that the few times it did happen, it was never a problem / actual downtime.
One thing to note is that there are some scheduled maintenances were we needed to react.
Yes, you can also run such a system based on donations. But I personally think that such a system is important enough to be paid for by the government. When you run on donations, there will always be conflicts of interest and the risk of running out of funds.
But yeah, Mitre being a private organization that was paid for by the government was a problem.
One thing to note is that there are some scheduled maintenances were we needed to react.