Do you mean a random gem working within a Rails app? That's a bit different, Rails conventions have changed significantly. A random gem might be an old gem that used old conventions, doesn't mean it wasn't quality at the time.
Maybe I should have said any random combination of gems. Monkey-patching is fine for a small-ish ruby script, but start combining ActiveSupport with some others and you quickly run into weird order-depending loading issues because of the Monkey-patching.
I've found namespacing to be the solution and it doesn't really cause me too much friction when coding either.
In the past 3 years that I've used Rails I've used tons of gems. I've seen exactly 1 gem in total that was messed up by the presence of ActiveSupport. I'm really wondering where you got the impression from that monkey patching is such a big problem.
