Until G&K, i couldn't fathom NOT going for liberty 100% of the time. The free settler as the second adopted policy and the finisher on liberty was a slingshot of epic proportions.
Usually, i'd time the completion of the liberty tree with researching theology. So the free engineer from the liberty tree would go to rush-buy Hagia Sophia, and the free person from HS would go for another Great Engineer to build another wonder available at the time, usually Notre Dame, or Machu Picchu.
- Mercantilism, also, was crucial back in vanilla. Massive happiness bonus for those inevitably important trade routes. Still crucial for wide play - it is essentially the same as order's opener.
As you can see, i always played wide back then

- Right now it's changed around a bit though. The free settler comes signifcantly later into the game now in terms of early expansion. I've also had a couple of games with the 4c/tradition start and it is truly quite a powerful way to play.
So anyway, nowadays, still adopting to types of play on G&K, i think i'm leaning towards agreeing with the original poster. The Rationalism opener is usually always easy to grab, grants a massive global science bonus, leads to other very useful policies. The only situation where it wouldn't benefit much is if you're already investing in Piety. In that case, the Commerce opener isn't bad as it also leads to other great improvements (dependent on context, obviously, as everything else in civ. Though the +3 in coastal cities and the virtual great lighthouse bonus in there is MASSIVE in Archipelago - especially if you're England!) that usually fit well even in pangea map. Stacks well with tradition.
Also, the right side of Commerce is quite powerful. Road maintenance is often relevant, 15% off purchasing in cities is also great, especially if you can combine it with Big Ben (i usually save a GE for this) - and especially the Lux-happiness bonus is HUGE now. Usually arriving at the point where you're shipping around something like 10 lux resources, it's effectively +20 happiness!