I wanted to say VLC because to me, it's the gold standard of fully working open-source software that just destroys the commercial competitors.
But it's not perfect only because society changes. New video formats forces VLC and open-source devs to adapt. Bigger video and new tech specs require VLC to update. If it wasn't for all those external needs, VLC would be perfect.
Did I also mentioned the many times rich companies wanted to buy VLC and they laughed?