I suspect that if people didn’t want the boozy taste, you could heat the liqueur in a pan and boil off the alcohol.
A number of liqueurs completely loose their flavor when boiled, I’m thinking specifically of Frangelico, but others are similarly affected.
But I guess that raises the question: what do we gain by adding a liqueur to a cake? Is it merely the flavor that exists independent of the alcohol, or is the alcohol an essential aspect of the flavor?
The alcohol is a necessary carrier of delicate flavors, but I suspect you already knew that. Also, the alcohol helps with attracting moisture and keeping the cake preserved/fresh. That’s why fruit juice can be a nice substitute, because the sugars are good at attracting water. Ditto for caramelized sugars, which make a great non-alcoholic syrup for chocolate cakes.