I completely empathise with all your views and your frustration is tangible. I had the same experience at my local wetland in Worcestershire (owned by the Worcestershire WT) - namely Upton Warren.
I was always criticizing the lack of care and thought for wetland birds and the habitat was deteriorating rapidly, in fact the site was being neglected in my opinion. In the early days me and a few birders resorted to guerilla tactics, ie chopping trees down in the middle of reed beds and altering the water levels by digging channels, building a dam and sluice, so we could drop the water levels. In time we met the Trust and formed a management team amongst the local birders. This was 30 years ago and we had to really push the birding aspect of the site and its true potential. It was a hard slog full of frustration and unnecessary bureaucracy, although to be fair these Trust are constrained by planning laws that are total bull s***.
However the one thing they all seem to have in common is the lack of foresight as to what could be achieved. There are very few birders in these county Trusts, so they don't see the same picture as we do. But if you learn about the habitat yourself and start putting plans to them that you can back up with facts , then you can get your point across and change things. The wheel does not turn quickly in the conservation industry, but be patience and persevere, but be prepared to get your hands dirty and muck in together with like minded people. At Upton Warren the birders manage and run the reserve ( under the auspices of the WWT. We have achieved a lot in those years and now have avocets breeding and other unusual species for an inland site, its not always smooth running , but ultimately we have achieved goals that would have been but a pipe dream 30 years ago.
Don't give up, formulate a plan and approach the DWT, this is what I did 30+ years ago. Finally forcing them to listen and changing their attitude towards wetlands and today relations with the WWT are pretty good.
BEST of LUCK Lads
B

John