I think more likely the large companies which provide "self service" will continue to dominate the majority share of the market while leaving room at the edges

I think more likely the large companies which provide "self service" will continue to dominate the majority share of the market while leaving room at the edges for other companies to differentiate on customer service. You can see this in effect with FastMail and Proton Mail each of which offer a great product in their own regards, but also have the major selling point of being "Not Google".