Whether you like it or not, there is a math to music. Making it not "completely" subjective.

1) Tico's playing has become less intense, and is playing quieter. This is of course natural due to his age. However, he is no longer at his peak. The volume and intensity of Tico's playing is not subjective.
2) The musicianship and overall integrity of the song have decreased. There is a way more formulic stucture to their music, making it much easier to replicate than normal. Things such as pinch harmonics are missing.
3) Jon's vocals have degraded to the point of him singing off key for a lot of songs. Singing off key is not a "subjective" thing.
4) Incantation of lyrics are worse. Less syllables being sung means parts of the original song is lost. That's not subjective.
5) Complete lack of variation of setlists, even with shows in the same city. This is the worst it has ever been. Again, this is a fact and not subjective.

peak: reach a highest point, either of a specified value or at a specified time.

This is NOT Bon Jovi playing at their peak.