How to blend medjool dates in a blender to make a pie crust?

I also recommend soaking in boiling water, and adding a few drops of it while pureeing, too. I prefer the food processor, as the dates are less likely to get caught in the blades, as with a blender.

In addition to soaking, I would add a little bit of baking soda to the water. This helps soften the dates (alot). But a small amount, ~1 tsp baking soda per 1lb of dates. Soak about 30-45 minutes.

Soak the dates in boiling water covered for 30 minutes and make sure they are roughly chopped for ease of movement in your blender/processor. Makes them far more workable and will allow the blades relative free movement

Dates are hard to blend into a smooth paste in a blender, even a high speed one. Soaking the dates prior to blending and making sure there is some liquid in with the dates may help. And don't overload the blender jar; you may need to split the ingredients up and work in batches. I also find that I need to stop and flip the contents of the blender (so what was on the top is now on the bottom) so that the dates on the top get blended more smoothly.
What else are you putting in with the dates? I've found it works better to blend up my additions first and then add the dates. If you have a food processor, that may work better. I don't have a food processor (mine died several years ago and hasn't been replaced yet) but I've been contemplating getting one for blending dates.