Mobile design was something created for old phones that didn't have quite the resolution of computer monitors. Modern phones don't really need mobile designed sites.
You need text to scale and reflow to device width if you want text to be readable. This is one of the main reasons for mobile web design. Else you're stuck panning around the screen to read the text zoomed in.
Once you decide to scale text to device size so that it's readable, you are stuck doing the rest of mobile web design (fluid layout).
You need to allow users to scale text as desired, as the original web intended. You shouldn't make a site targeted to mobile; you should make a site that allows the user to display in their client as they wish.
To solve that, you have to move from the easier static made-for-one-width design (what we think of as desktop-first design) and move to fluid, reflowable design which we tend to call mobile-friendly design.
Unfortunately, it tends to take more thought because we usually want widescreen components, like sidebars, that are easier to build when you can hard-code a device width, and hard-coding width is what breaks zooming and text size changes.
