Is it secure? Hm..I'm sure Salesforce does more work around security than the vast majority of their customers would even be capable on their own.
Similarly, these types of catastrophic events will happen and I am just as confident in saying that Salesforce was able to diagnose and fix this problem better than the vast majority of their customers would have been able to do on their own systems. I've seen JIRA on prem go down several times.
I've worked building enterprise applications my entire career. Unless you have an extremely lean and engineering oriented organization, it's almost always better to buy than to build in house. There are exceptions, but for the most part this holds.
Having said all that, every single place that I've worked at has had it's own data lake/warehouse and having your own backup of your data is critical.