"The bitcoin network's theoretical maximum capacity sits between 3.3 to 7 transactions per second."
The solutions for this 3 hour backlog of unconfirmed transactions include: implementing SegWit, increasing the blocksize, and Lightning Network.
Edit: after refreshing the page it still had about 220k pending transactions but was doing ~11.34 transactions per second. Equating to ~5hrs.
Edit 2: Again refreshing it went to 24.61 (2.5 hrs). Another refresh went to 11.56 (5hrs). So there are some clear stability issues. But your max of 7transactions/second comes into question, or this site.