Yes I am not surprised your friend had problems with Wix it’s a pants platform.
As I said there is a market out there and there are fair few web ‘designers’ already specifically targeting hosts, so it’s about you identifying how you add value and what you can offer that others can’t.
Wordpress provides free plug-ins for SE0 and I would hope anyone building their own site would know to use tags.
Quite honestly I am not teccie at all and I can knock up a Wordpress site fairly easily using the huge selection of free templates they offer, so I can’t agree that it’s that hard.
However I agree that there will be people who won’t have the inclination to do it themselves, who would be your target market.
What is your competition charging to build sites in Wordpress?
By the way I don’t have a website for my listing, as a) I get all the bookings I need from Airbnb and b) I don’t have the time or inclination to vet direct bookings and do the paperwork, I much prefer to pay Airbnb a minimal fee to do it for me.