I think you are mixing up hosted channels (virtual, no chain footprint) and 0-conf channels (node giving you the ability to spend/receive before channel opening tx has the first confirmation)

I think there is a decent size of huge channels connecting some of the bigger players that might be unannounced (priv channels), but not necessarily completely cut of from the rest of the network. There is very little upside for doing that unless you have a completely closed ecosystem, which is hardly ever the case.

What you call decoy nodes are also very practical for various reasons, first of all plebs will give you lots of capacity due to the brand name and you can make sure you are well connected within the network, but you want to keep the node doing any kind of business activity separate so you don't have routing revenue etc polluting your accounting books, you just do one (or two just in case) priv channels to your routing node from the business node and do the actual payments from there.