It removed the physical function keys, which is a huge no-no overall. The initial version also lacked a physical Esc key.
But the bigger issue was the notion that it was created in spite of having a conventional touchscreen on the laptop instead. Apple has been rather weird, petty, and immature about putting touch on Macs, stemming from Jobs' ill-conceived "your arm gets tired if you have touch on a laptop, boo hoo" speech which has never been correct and continues to be misconstrued as scientific when it isn't.
Luckily, the market soundly rejected the Touch Bar and Apple is now due to release Macs with proper touch on them. It took a while, but this era of pretentiousness is over.