The right amount of specialization can make it easier to market your business ("we do web dev using the highly performant x stack...") and get better paid ("... and we're one of few with y years of experience of doing it so we're pretty great at it"). You can be very specialized and still find enough work if you're willing to work globally.
In my experience it can be challenging to communicate the competitive advantage of a particular language let alone framework; most businesses don't care about such details. If so, you need to bring more value to the table, such as that you're one of few using x stack that solely work with e-commerce, that your web marketing skills are exceptional, etc.
What would the difference between doing freelance work and having a consultancy actually mean in this case?