Am I right in thinking then that these would be the top 4 priorities for a BL RPG?
1. Large map with good sense of atmosphere
2. Fun/engaging systems
3. Simplicity
4. Fast progression
Speed of progression isn't necessarily the issue.
It's the method of progression.
If you're doing the same thing over and over for a couple of weeks, not only does this enable easy grinding bots, but it's also so boring that people are going to have more fun making bots.
Meaningful progression helps. Instead of getting your stats raised, or meeting some odd tier thresholds... Would be more beneficial to unlock new and exciting things, as well as doing a variety of things to progress. And every little feature doesn't need it's own level.