I have walked long distances in Shimano leisure shoes and boots , the ones with rubbery rather than plasticky soles. They may be thin but they are very comfortable. I used them without cleats , in toeclips. Cleats may affect the comfort and grip.

Note that any clipless shoe has a failure mode: the fibreglass midsole cracks and the cleat cannot be secured. This failure is not very common but has happened. Many long distance expedition riders use toe clips and trail shoes or boots for versatility and better failure mode.