I have updated to Lightroom 2015.2.1 on a Mac Mini (2015) 8Mb memory. I have been trying to import material from a local NAS. The import routine is appalling, it is slow to the point of being unusable, it is convoluted to navigate (I don't want to see pretty graphics I just want to import RAW files) and just when you think you've got there it crashes. Am I really paying for this. You had a perfectly usable product and it has transformed into a monster.
Please go to the Preferences of the Lightroom under the general tab uncheck the option"Show Add Photo screen".
Restart the Lightroom and try again.
Many thanks Deepak
Some improvement by removing the graphics and at least helpful messages are visible but overall performance is slower than before the upgrade (by some significant margin). On Friday used Bridge and ACR to get over the immediate issue will probably roll back to last version using official guidance until next upgrade.
Once again, many thanks for help.