If by 'glory days' you mean sales alone, then yes that's true (and not at all surprising). I look at it from a different perspective, (because I don't have to worry about revenue), and I think that the band can still produce quality music.

Jon has all but admitted that the last few releases have been a Jon Bon Jovi & Shanks collaboration. There have been some gems on those ventures too but the return to a band production, to whatever degree that may be, has borne fruit.

Some of the glory is still there to be tapped into :)

Kids is their second single. The lead single (Wherever I Go) has 144m. Remember when they supported Jovi several times in the 2000s?

It's better to compare Jovi against other veteran bands (active for 20+ years) and their recent lead singles:
Red Hot Chili Peppers - Dark Necessities - 48,2 m
Blink 182 - Bored To Death 33,2 m
Green Day - Bang Bang - 8,1 m
Metallica - Hardwired - 7,9 m

So yeah, they're pretty screwed at this point. That's paying the price for 15 years of market over-saturation.

But they have been released in the same time as THINFS?

Green day was the same day. Not sure on the others.

It's not quality that's the issue, it's just about getting picked up on a Spotify playlist or radio/tv. Green day seem a few years younger than Jovi, they are at hand/lh stage of their career I would say

Is Metallica though? Nope, they're even older. But they are in those playlists, because them putting out new music feels like a big deal.

Green Day had new music in 2004, 2009, 2012 and 2016.
Metallica: 2003, 2008, 2016
Bon Jovi: 2002, 2005, 2007, 2009, 2013, 2015, 2016.

I didn't say quality is the issue. It's the frequency of releases. And when they are as frequent, they receive less and less attention; thus contributing to the reputation of being mediocre. Jon is too productive for his own good.

Green Day and Metallica yes, the same week actually. RHCP and Blink songs are 2-3 months older, but let's be realistic. THINFS will not get even close to these numbers even in a year from now.

What really scares me is the fact that the whole album was writen to fit the state of his voice, so he's doing ok on thise songs (though he lets the band tackling a lot of vocals during choruses, check out THINFS as an example), but what is he going to do on the classic songs? He needs to take lessons like back in 2010, maybe that will help. Or it's going to be painful. And he knows it, hell he even wrote a lyric about it on the album.

I'm sure Jon works on his voice. But no amount of training will get his voice back to sing the classics how they were recorded. 2010, 2011 ( The Greatest Hits Tour) he sounded good, unfortunately 2013 (WAN Tour) was mixed and 2015 short asia tour was horrendous.

THINFS isn't difficult for Jon to sing, due to him writing around his voice like you said. The classics he will always struggle with, you just have to wish for the best when he performs these. But Jon can sing/write good songs just look at THINFS Album. It's highly unlikely Jon will have Vocal surgery, unless he really wants to, but why? THINFS is what fans should judge Jon on now carrying on, not the past.

If Jon can produce a HAND, TC, and THINFS type of songs in the future I will be happy, it's the best we are ever going to get from him. Also as your get older you don't write the songs you did in your 20's or early 30's. Like Jon has said it would be stupid to rewrite or do something similar to livin' on a prayer at his age. Even if he did have that voice, I doubt he would have written a song like that today, but we will never know.

Metallica is a different genre. If BJ put out a rockier album and promoted it as such, I think there would be a bigger hype.

Jon isn't capable of Rock anymore not what he used to do in 80's/90's.

HAND, TC and THINFS is the best he is capable of, unless he decides to ever have voice surgery.