I still collect game CDs, I've cut back. I once tried to get every single Final Fantasy release, no matter how rare or exclusive. Now, I only buy the major ones and don't even bother trying to track down the LEs, promo dics, or retailer exclusives. Similarly, I used to collect all the Tales OSTs, but I stopped doing that a few years ago when the yen got strong. They weren't bringing me any joy and I was only buying them because I bought the other ones, so I dropped that series entirely. Now that the yen is weak again, I've been splurging a little more than I should, but I'll pull back when the yen strengthens again.
I totally respect those who have moved to buying game music digitally (or simply streaming it), but I like the fun of collecting and having something to hold and put on my shelf. Having a bunch of sound files on a hard drive doesn't do anything for me, even if the music is just as good. I suppose I will stop buying new game music once the CD format is retired or I can no longer by optical disc drives for future PCs, but for now I'm still keeping up with major releases.
As to why discussion has trailed off so much, I think the rest of you have hit on all of the major reasons. In particular, I think the ease of sampling has really taken its toll. Back in the late 90s, it was always exciting to read impressions by forum members who got the latest albums. You got to know who had similar tastes to you, and when they recommended something, you really looked forward to getting the CD in the mail and hearing it for yourself. Back then, Square's upcoming PSX games were the stuff of legends, and listening to the music months before the game came to the U.S. was thrilling.
As someone else pointed out, the decline of the Japanese game industry has had a knock on effect on this hobby. Most major game CD releases these days are just arrange albums of stuff that was popular 10 or 20 years ago (I'm listening to Bra Bra Final Fantasy as I write this). They're still good arrangements, but the newness is notably absent. I think Bravely Default was a rare gem that came out of nowhere a couple years ago, but albums like that are the exception these days.
There is a lot of great game music coming out of Western indie teams, but so little of it makes it to CD that it's not really for collecting, and nobody talks about it because you can just go to bandcamp and download it whenever you want. There's no more thrill of the chase, no more nerd pride in having something special. The democratization of game music is good for music fans, but it's taken it's toll on communities built around niche collecting.
To contrast, notice how hot amiibo collecting has become. A year ago, amiibo were just weird curiosities Nintendo was talking about, but today there's TONS of internet discussion around them. Communities naturally form around shared interests of scare objects of desire. If Nintendo ever catches up with demand or (more likely) when the fad blows over, those communities will disband as quickly as they formed.