Sure, you can rattle off scales and string riffs together and throw in the odd mode or two, but unless you’re thinking melody, you have not made music; you are not improvising. You may have confirmed that you know which building blocks fit, but you’ve created nothing new. Improvisation to me implies invention, and you don’t invent scales any more than an artist invents Cobalt Blue or Vermilion Red. Scales and modes are like the squirts of paint on a palette. You have to choose carefully which to use, which to blend. Start mixing too many colors and you wind up with mud.