Well, not really - when you're looking at a waveform, you're seeing a zoomed out summary of the data on disc. If you zoom in, you'll see many more details and gradations that you couldn't tell from far away. It's kinda like trying to describe all the beaches of California, in detail, by drawing how the coastline looks on a map of the U.S.
If you zoom really deep down you'll get a more accurate picture, and yeah it would be possible to create music that way - but drawing at that level would be extremely tedious and time consuming and likely impossible for the average human.
To understand why - it'll help to do a little napkin math to get the possible variations, and we'll see that they become too enormous over the time of a song (and what is music if not creative choices over time).
Let's assume a relatively standard digital format - 44.1khz mono at 32bit depth.
That means the value can change every 1/44100 or 0.00002267573 of a second - and that the possible values at that interval are between 0 and 2,147,483,647 (though this 32bit range is usually represented as a floating point range between -1 and 1, the possible gradation is there)
So, given our chosen file format (44.1kz 32 bit mono) - in order to be able to actually paint music with control, it means you need to make creative decisions among 2,147,483,647 choices every 0.00002267573 of a second. Otherwise, the strokes are too broad to be conscious. That's 5,682,241,729,962,000 possibilities for 1 minute of music (2147483647 x 44100 x 60). Zooming in and drawing and fine tuning to creatively control that might be possible, but it's impracticable.
That said, there are a number of other alternatives which allow you to "shape" the waveform in larger sections without being so brutal. For example - you could have two sine waves of different frequencies and/or amplitudes and/or phase, and add or subtract them... this is a whole other topic of things like additive synthesis, but the general idea of thinking in terms of shapes rather than notes does allow for some interesting tooling (though imho it's more on the side of creating virtual instruments and gear rather than music composition)