Apples and Oranges.
First and foremost, if any of us are as genius as Mozart, Beethoven and the others listed, then wow! Make the most of it.
The great composers were writers and performers of extraordinary music for the time (and forever, I suppose). They were full time musos (for the most part). They were not recorders as we mostly want to be. Recording takes way more time than writing. I have written songs, choral works, music theatre, orchestral works etc. over a very long time. I have recorded a lot of it to a certain degree of clarity and success. But, I really need more time and financial assistance in order to make the recordings as good as possible. Stuck in my home studio, I do all right for my tastes and wants and needs but to take my work further requires so much more. Plus, I work nearly full time which takes away a lot of energy.
The real question one should ask is what would these great composers have done with the technology. Copy and paste happened even in their time, except it was hand written. Listen to the Messiah, for all of its merit, there’s an awful lot of painting by numbers in the orchestral score.
Still, comparisons are impossible. Apples and Oranges.
all the best
Jonathan