3-2-1 Ribs

Too hot and too long. You might can get by with 3-2-1 at 225.

At 275 I think I usually run a 3.5 hour cook time. More like a 2-1-.5

Every rack of ribs is different. Use 3-2-1 as a guideline for the following:

3 - Cook until you like the color
2 - Wrap and cook until the meat retracts, exposing about 3/4 to 1 inch of the bones. Practice will let you determine how to get the right pull based on the amount of exposed bone. At this point the ribs are cooked.
1 - This is for finishing and putting on a glaze. The ribs may dry and firm up a little. I somethimes shorten this segment to 30-45 minutes when I don't use a glaze.

Def depends on what type of ribs. For baby backs I do 2-1.5-1.5 @ 225. I started out doing 2-2-1 but found the wrapped 2 made them too tender and you couldn’t even handle them after pulling out of the foil without them falling apart. So I found my mix is great for having them pull back off the bone but not too tender. If I add sauce to them I add it with 45 mins left in the last 1.5.

1-2-1 is my sweet spot.

6 hours is wayyyy too long to cook ribs.

There's nothing wrong with your cooking temperature at all. You can cook ribs anywhere from 225-350. There's more variables than just a generic timeline. There's some missing info here.....what type of ribs, how much did they weigh, fat content, type of smoker, was there any additional humidity present, how often did you open the lid/door, how long did you leave the lid/door open, and how long does it take for your smoker to recover your cooking temperature?
Don't worry, keep practicing, and most importantly....enjoy the process