Too bad, there are some really great features in iOS 10 that I love. I won't be using the POW / BLAM like batman either, but the minor 1-2 times someone may use it to send me something is not enough (for me) to lose out on the great stuff in iOS 10. Plus I will be stuck, since I can't take the iPhone 7 coming in Friday and go backwards anyway. But if you're waiting for Apple to give you an on/off switch.. I personally think you'll be on an old iOS until the phone dies.
No it just means other options are on the table when I upgrade devices. Like I may get an Android Phone and replace my Windows Notebook with a Chromebook and my iMac with a Windows PC for gaming. Etc.
I would just change my device composition and move on, just as I did when I got an iPhone. My iMac and other Apple device purchases were spurred by me moving to the iPhone. The same thing would happen, quite quickly, if I were to move away form it. I would just reverse it. The money I'd save getting a ChromeBook over the MacBook I was planning to get would virtually fund the rest of the move, so I'd probably do all of this in an afternoon (one shopping trip once I changed phones).
For the moment, I don't see a point in upgrading devices or FW on my current device, and since the old version isn't that old I will have a year or so to plan out a migration if I want to be lazy about it.
Also: How much this will bother you depends on your social circle. I don't think it's sexist to imply that women are more prone to overusing these things than men are, because my anecdotal experience, this has been the case. If you communicate with women a lot, they tend to use things like stickers, emoticons, etc. a lot more than men are. So, your experiences can change depending on the age groups, genders, and settings in which you communicate with other people.
Not saying this will be the same for other people. I just know what I'll be "walking into" if I install this on my phone.
It's something I'm wholly uninterested in putting up with. I am not in the business of dictating, to people, how they should use their devices when communicating with me. I rather isolate myself form it in other ways (Deleting Facebook Account, not installing the FW update with the offending features when I cannot turn them off on my end, etc.).
When Facebook added stickers, it completely ruined their messenger service for me because people stopped using words to communicate in many places, and you simply had no idea what the stickers "actually meant" when they posted them. The stickers also take up as much vertical space as some small paragraphs of text.
I don't want my phone making noises or doing gamey effects simple because I opened a thread, and I don't think having to 3D touch and pan over an image to see it is a feature I find... useful.