Fingers

It would seem self evident,and I would have thought the accordion would be a prime example
The cheaper Chinese boxes,invariably come with the caveat "harder to play"
And It does make one wonder,how many people have abandoned ,playing because of difficult to play or dreadful sounding instruments
If everyone were given a brand new Bugari Juniorfisa 48,as their first beginners box
I think a lot more people would persevere.
I agree that the player is the most important factor,but an instrument that is slow to respond,poorly set up.
Opposed to a more resonant,easier to play instrument is just as important,poor instruments create limitations.
On an entry level violin,replace the dreadful strings they come with,
put on a set Dominants you have a completely different instrument.