As with so many opinions these days, it's at one extreme and ignores the middle ground.
For some apps, the big issue is when you schedule the downtime to happen. If you are truly customer-centric, you should schedule for a time that causes the least disruption for your users. Of course, a decision like this depends on other factors - the number of users likely to be affected, how critical the app changes are, costs, etc.
I've noticed a number of companies in my country taking sites and apps offline in the middle of the workday when they're very likely to be in use. To me, this is unacceptable - the work on the app should be done after hours.
Surely this is up to the company? They make a decision as to whether to pay somebody to work after-hours versus the business they lose by not doing so.
I specifically took a job that didn't require after-hours work (I have a family which I prioritise) and we did upgrades in working hours. Once in a blue moon a site would be down for a minute or two, but the trade-off was obviously worth it for my public sector employer which generally struggled with recruiting engineers.
For some apps, the big issue is when you schedule the downtime to happen. If you are truly customer-centric, you should schedule for a time that causes the least disruption for your users. Of course, a decision like this depends on other factors - the number of users likely to be affected, how critical the app changes are, costs, etc.
I've noticed a number of companies in my country taking sites and apps offline in the middle of the workday when they're very likely to be in use. To me, this is unacceptable - the work on the app should be done after hours.