Looks like a lot of us are in the same boat...
I started playing in January 2016 and I've been in the same guild since the beginning.
We've slowly built it to almost HSTR ready now (96.50%) but it's been a long way... maybe too long. I must admit, I thought about leaving and going to an HSTR-on-farm guild quite a few times, would have been much easier to just participate and get the rewards, rather than having the headaches of managing people and events. Well, on one side, it was worth the effort.
We tried to merge with another guild last year but that move failed during negotiations, we both needed 10-15 players only.
TW - we win most of the time but only because we have a good strategy and are very keen that people deploy just the teams required in that territory, no "it's up to you, put whatever, just deploy something".
TB - most of us do everything but a few people can't be arsed to even deploy (well, couldn't, as they got the boot).
My problem is with joining a guild though... something's fishy, I keep saying it and the guys must think I'm a bit crazy...
We have been 42/50 for about 2 months, nobody joined; all of the sudden, last weekend we had 8 people joining, from different guilds... and it's not the first time I noticed this issue. Maybe it's in my head only... :)
It's very hard to have consistency at a high lvl, unless you are a strict "elite" guild focused on progression.
People will come and go, it's the natural way but the direction the game has taken for the past year (or so) doesn't help either.