Very valid points here. I haven't played Live so I am no way prejudging the game however I think people can play Live 15 and immediately recognize the improvements both with visuals and gameplay. Because of this it is easy for people to say "Wow look at how much better Live is. EA put in so much." And like you said that work had to be done. Few would consider Live 14 a good game so if minimal improvements were made the series would be in severe touble.
Now, in comparison, the 2015 edition of "the competition" does not have improvements that jump out from the get go. I am a fan of the series and my first reaction when I began playing was "ok this is very similar to last year." As I continued to play more the changes became more evident but the are subtle changes that the average fan might not pick up on. Because of this I think people look at the game and say "The game is barely changed. There are still so many unaddressed issue. The company didn't put in any work."
It is really just the tale of two different games, and I am not talking about the play styles of the games. One game is playing catch up and needs to make big improvements to stay viable. The other game is in the driver's seat and doesn't need huge improvements year after year. It is not without flaws and could see bigger improvements on a year to year basis but the improvements aren't a necessity for the game to survive.