On the flight here, someone commented that the 737-800 we were on was “the smallest plane [they’d] ever been on.” Someone here just commented that today’s 737 is “not a very big plane.” What are airlines flying around these days?!?

Well, if most of your flying is intercontinental or inter-Asian, it's plausible...

Narrow-bodies are becoming more common in Asia because of the low-cost carriers and the pressure they're putting on prices.