This is a graph of comments posted on my videos according to time. It starts with the formation of the channel and ends today. You can see that the amount of comments in the last year and a half are dramatically down. The thing is, this is not just true for me but for most people I know - even some of the big names are dropping in interaction like crazy. Seems YouTube is turning into a TV style platform where people don't care to interact.
Subscribers across time. Same time frame as above. You will notice 3 very large drops. These happen at random and have hit a great number of content providers over the years. YouTube now and then "cleans out" the dead subscriptions. The only thing is now and then it all goes wrong and it drops a large amount of active users as well. I know many times I have had to resubscribe to a channel because YT just decided I should no longer be subbed. For literally 2 years there where 6 people who it would drop me from every 3 months like clock work. This seems to have stopped but it still happens at random now and then.
Some have said the trend of the big names to literally never reply to any comments is to blame for the lack of comments this last while. I don't know. I just know that people have stopped commenting. Even people who used to comment on every video now only comment once a month or so.
They are making it harder and harder to make any money unless you are a verified content provider with a large amount of subs and stick to the ever changing and baffling rules. I have seen people I know get ads removed from videos where they did nothing wrong and there was NO risk of anything being "controversial". Most of these people have literally stopped using the tags because it is a source of problems with the bots. So completely family friendly videos are being told they are not suitable for all audiences.
sooner or later YouTube will either fail at this rate (they are bleeding money) or they will have to change to a professional entertainment service. It seems the latter is what they are trying to do and are going about it in a manner where they try to force the small people off the platform.
In the end there will never be anything like the good old days on YouTube as the many other platforms that sprang up have not come to be popular to any great extent. Even if they do, like Dailymotion people may view a lot and you may make a few bucks, but they literally never interact with you. So the old days of fun and excitement and the hater hoard seems to be over (All they do now generally is dislike with sock after sock)...