I prefer to design my own systems these days. Even when I play a published RPG, I modify the hell out of it. I couldn't possibly DM 5e by the book any more. I really dislike so much about it. I'd need about 10 pages of house rules to make it tolerable.
I actually like the freedom of the cypher system. I switched to it a while ago and I must say it's always difficult to go DM back with more elaborate and restrictive rulesets.
Cypher system is great! Really easy to teach to new players, really flexible. I used it to run a game about modern-day real world street kids facing an alien invasion.
