My 2012 N7 has been slow for ages
When I first got my Nexus 7 back in 2012 it was a speedy little thing, and remained so until earlier this year. Android 4.4 didn't slow it down, but sometime around this summer maybe it slowed to a crawl, errors would spring up about applications not responding, and the thing would take forever to start up, open apps etc. especially when compared to my Nexus 5. I tried reflashing it, performing factory resets and so on but nothing seemed to help. From looking on sites like XDA Developers and Android Police it appears that the issue is to do with the NAND storage the 2012 Nexus 7 uses - the 2013 model is supposedly unaffected.