When I used to play a caster Ritualist before, the piano playstyle immediately made me dislike the build.
Then I figured out I can just use X-Mouse to make my left-click do its original purpose (use the skill assigned to it) while repeatedly executing simulated keystrokes as well (press keyboard keys where other skills are assigned) as long as the button is pressed down.
You can even add delays between keystrokes (to allow for some skill casting animations to complete before the next one) as well as delays on repeating the whole keystroke cycle while the mouse button is held down (to prevent X-Mouse from immediately repeating the same keystrokes especially for skills with cooldowns).
For keyboard stuff, AutoHotkey is your go-to.