Without quoting specific rule changes, most of which are in your link, the big ones are: prohibiting contact on eligible receivers outside of 5 yards of the LOS, ever increasing protections for the QB and WR against big hits and the loosening of what constitutes holding along the offensive lines.
Basically, you have a hard time being physical with the receivers, threatening them with big hits or using them to dislodge the ball while top QBs are easier to protect, difficult to intimidate and stay on the field longer. This has helped the passing game, which has added to interest in the sport, IMO.