Short Answer: It all depends on what you are going for and the size of your stash.
Long Answer: It is hard for many quilters to move past kits and past other people's designs. I understand the lure of kits, I get a great deal of satisfaction when I have gone through my stash and prepared my fabric, cut my pieces etc., and I have it ready to sit down and sew -- it's a lovely feeling, like a present to myself
When you are selecting fabrics to use, keep in mind what you've learned while making those kits and what looks you want. A lot of people over coordinate their fabrics in my opinion and to my eye the results are bland and washed out -- but to someone else it is exactly what they want! Personally, I tended to buy a lot of "tiny viney" small scale prints and had to learn that I like contrast in scale as well as value and color. I have vision issues and prefer sharp contrast because it is going to look fuzzy anyway...
At this point in my quilting, almost everything I make is scrappy to some extent, but it is planned. I started about 40 years ago before the rotary revolution and don't come from a family of quilters so am self taught and didn't grow up with quilts. Judy Martin's book Scrap Quilts really changed how I viewed them (scrap quilts) and was a big influence on me when it came out because before then I hadn't seen scrap quilts that I liked, only ugly "use" quilts.
https://www.amazon.com/Scrap-Quilts-.../dp/096029709X
For me I started thinking more in terms of "values" so light, dark, medium which can be any sort of print or style or color. Or you think in terms of color groups, or style of fabric -- there are many routes to go.
My current quilt will be 42 different purple fabrics in the blocks (one per block) and then a set of half blocks and some plain fabric for the border in a 43rd fabric. It is a tessellating two-color star/pinwheel design. I'm using white-on-white fabrics for the non-purple part, each block will have the same fabric within it, as it happened to be easy to cut to where I will have no more than 4 blocks with the same fabrics, and I have a piece big enough (hopefully!) for all the border units.
But the next scrappy project will be using civil war fabrics, a different palate and style. I used to do a lot of fabric swapping around Y2K and I have a bunch of 10" squares to use, so need to do something with a lot of variety and small pieces. In that quilt each piece of fabric will be random in terms of what fabric I use, but placed in the block by value (dark corners, etc.) with the goal of having every piece of fabric in any given block unique, but using the same fabrics in more than in one block especially with different shapes and sizes. To me I find this look rather chaotic but I think will work with my available fabric better than piecing each block with 4-5 coordinated fabrics and is the right thing to do. But I've been mulling it over in my mind for some time, my natural inclination is to add fabric by different blocks rather than within each block, but I've gone all over wild before with great results.
I also do charm quilts, where each piece of fabric is unique. That's a whole 'nother kettle of fish in terms of design considerations and such. But you learn that if you throw enough fabrics together, it works. For me though, it actually works with a lot of effort and tricks I've learned through the years. If you go random, well random can result in ugly. I think most quilters want aesthetic randomness, which isn't exactly random.