4e may have been the last straw, but I was almost ready to drop 3.5e all together back in 2005. Stat blocks were killing my creativity, along with a number of other things.
3e/3.5e is fun when you're the player--you've got lots of options to build your character. But it can be a chore to run as a DM, who has to keep track of all of those options.
High level games made me tired because encounters took forever as players waded through all of their skills and powers. Then, in turn, I had to figure our what my own monsters and NPCs were going to do. If you didn't get that right combination of feats and powers in, they could be a pushover.
After 2005, I ran other systems for a short time, such as Warhammer Fantasy Roleplay, AD&D 1e, or Castles & Crusades. But my players didn't like those.
So I ran 3.5e. To reduce prep-time, I based my campaigns around published adventures. I photocopied stat-blocks and NPC from other sources. I used the stat-cards that came with the D&D Miniatures line. Anything to keep me away from creating a stat block.
It didn't completely solve the problem--there were still all of those rules for everything to manage. The Rules Compendium, published in 2007, helped a little--but it also introduced more rules.
When 4e came along in 2008, I thought it was a solution at first. I bought the core books and tried running a campaign for three months. The end result: neither I, nor my players, liked 4e.
So I went back to running 3.5e, until 2011, because that's what my players would play. After that, I took a long break from DMing until I figured out what system I would run next.