Not-so-random Thoughts on Random Encounters
I think it's fair to say that encounter tables are meant to be tailored for your adventure, your campaign, your world. If something on the table doesn't fit, you're not using the proper table. The tables in published modules usually fit because the author(s) have selected creatures that make sense for the adventure.
Next: a random encounter doesn't mean a fight. That's what reaction rolls and reaction adjustments are for. (Remember that Charisma score you used as a dump stat...). Maybe the bugbears approach cautiously because they have recently been in one scrape and are in no shape to be in another. Maybe the barbarian encounter you rolled is a group who wants to trade. Tailor the encounter result to your game.
Again, a random encounter doesn't mean a fight. That's why there are chances of things that aren't "level appropriate" (Side note: there's no such consideration for "old school" games). If you roll a dragon, nothing says the dragon pops up in the middle of the camp site and breathes fire, immolating the party. If you feel a dragon would ruin your campaign, why can't the party just see a dragon flying through the sky, obviously intent on being somewhere else?
Use your critical thinking skills. Be creative. I believe in you.