On the evidence, yes. Cloud providers frequently have outages lasting multiple hours affecting millions of clients. Some governments manage to run critical servers without downtime.
But if I had to make an a priori prediction about which systems would have the better reliability over the long term - cloud-based or those run out of a corporate DC - my money would be on the cloud-based systems.
The cloud providers are going to have better management of power/network/hardware than the most mature government agency, simply because it's a core capability for them.
In contrast UK gov servers like hmrc.gov.uk (for example) are pretty stable, I can't remember the last time I heard about an outage.
Cloud providers are certainly better at some things (like staying up to date with latest tech), but I'd contend reliability is not one of those things based on their prominent and frequent outages (at least several a year).