I do agree with some points presented here, however the one thing I want to point out, is that you are honestly not the only person who goes through this. Every high-ranked, or well-known player has been through this.
Hell, I'm sure it happens to "little-known", or "low-ranked" players with lots of points, or a bounty.
This little point could actually change your perspective on a few things. With the mindset that "only you and a few others" know what it's like to be targeted, can lead you become even more frustrated. This frustration is why you think you're the only one who knows what it's like. When someone targets you, you wonder "Why me? Why not any of the other 23 people in this lobby?".
It happens to many people. There are 140+ staff members in this community, and I'm sure it's happened to all of them at least once. There are numerous VIP's, and numerous friend ranks, of whom I'm sure get their fair share of targeting, as well as just about any known YouTuber within this community.
Then, when you try to discuss it, others agree, and people who have felt the same frustration feel like they have it worse. It becomes a battle of "who has it worse".
Now, about the tactics you spoke about. These are new. Flint and Steel definitely hit the mainstream, and well, so did running. As much as you might dislike, and be frustrated by these techniques, part of playing MCSG is adapting to new techniques. Whether this be adapting to them, and leading them for yourself, or adapting to them, and learning to combat them-- if you wish to continue to play, and win, sometimes it has to be done.
It's a bit like when people say "Back in my day...". Things might have been better back then, but it's nearly impossible to go back, and you just have to adapt to what's new. Keep your "old" tactics, but learn, or adapt to some of the new ones.
MCSG has changed. Strategies have evolved, gotten worse, and mainstreamed. Sometimes, whether you like it or not, you just have to adapt. If that's something you can't do-- take a break, or remove yourself from it all together.
In the end, it's a matter of opinion. This is mine, that is yours, and choosing to leave-- it's understandable. Hopefully you'll be back, but if not, it's unfortunate this is how you've grown apart from the game itself.