OK, with tongue firmly in cheek, I will try to reply to your points from the perspective of the small organisations I was talking about.
But with a cloud-managed system you have a professional, single-purpose organization dealing with those challenges.
Just to be clear, are you thinking of the professional, single-purpose organization we've been discussing today in the context of a catastrophic data breach, the one we've been discussing in the context of incompatibilities with other vendors, lock-in effects and expensive licensing, or a different one?
Generally these systems only need internet connectivity to change the configuration and for some monitoring features
So as long as the equipment is set up exactly how we need it and never needs to change or be checked for any reason, everything is good. It's hard to imagine why these devices need a UI at all, when the engineer who installs the equipment could just set it up once and then you're done.
In practice, customers are okay with these being unavailable during internet outages as long as both the management platform and the ISP are on a pretty strict SLA.
John: Bob, the Internet is out again. Who do I call at the ISP?
Bob: We don't have a dedicated contact, it's just the business support number on their website.
John: I'm in the queue, at number 17. What's our maximum time for someone from the ISP to contact us about an outage? That might be faster.
Bob: No-one will call, but if it's not back by next business day we do get £50 off next month's bill.
(This is roughly how that conversation probably goes when you're a 20-person organisation with two floor of an office building on a business park outside a small town.)
(Compare, for example, the usual downtime from your 1-4-person IT team not having someone with the right skills on call.)
What's an IT team?
Who has the cash for that?
What cash? When we have a new starter, John or Bob sets up the WiFi on their laptop and company phone and adds those MAC addresses to the whitelist for the network. Normally John works in development and Bob works in sales, but they do know a bit about networks so this is fine. Well, as long as they can get to the GUI, anyway.
Small businesses whose core competence is software/networking, or who by coincidence have that expertise in-house, are a tiny niche market. No one [2] cares.
And yet as someone who has worked for software development businesses for an entire career and whose customers/clients have mostly been other relatively small organisations of one type or another, I have never met one that didn't. Of course that could be because I've tended to work with other technically-inclined businesses, but the same is true even for schools or my own business's accountants. I'm not claiming this is some sort of universal truth, but I don't think the market is nearly as tiny as you're suggesting, at least not in this part of the world (the UK).
Remember, we're probably not talking about setting up encrypted WAN tunnels across continents and multiple layers of switches in a data centre here. We're more likely to be talking about getting an Internet connection with suitable firewall set up, connecting a handful of switches and APs and making sure everyone knows the WiFi password, and installing everyday software on the staff PCs and mobile devices with maybe some basic configuration and enabling updates.
[1] See for example the rise of the Managed Service Provider, which was a large and growing subsegment for Meraki back in 2015 or so. Showing up, installing the hardware, setting up the wireless, and then managing it from your office a few miles away is a big business opportunity, and is a much more efficient use of limited skilled IT labor.
They're not unheard-of here, but again, in my experience such arrangements are far less common in smaller organisations than just having a couple of people on the staff who also "set up the IT" and know enough for the kinds of everyday admin tasks you're talking about.