If an mx blue switch lost it clickiness, is it because of the stem or the left?
Could be wear in the housing or the stem I think. It definitely can't hurt to try swapping out the bottoms.
For some reason though, I have a nagging feeling it's now likely the stem. But that's just my gut feeling at this moment.
The MX blues click is caused by that little white bit hitting the bottom of the switch.
Loss of that could be due to a small hair, fibre, grain of sand or liquid getting into the switch and dampening the internal movement.
If you are getting a replacement switch, you are probably looking to desolder the existing switch - so just replace the entire switch. They are plentiful, so you won't need to replace it again in a hurry.