Yes, quite unusable on El Capitan. Controls and screens don't refresh, frequent lock ups ... It's been quite a mess for while now. I switched to Airmail 2.
No, it's never too late. If you are motivated and hungry for knowledge, that is. I started my undergrad comp-sci degree at 26 and it changed my life completely. If you don't do it, assuming you wanted it forever, you will be regretting it forever.