The blunt truth is all products decline eventually.
However, you can stave off decline via:
Improvement - Faster, cheaper, nicer, easier to use
Refreshing things - New design, new packaging, new features
Find new users - Different group or for a new purpose
Reposition the server - Change the story about why it matters
What doesn't work:
Shouting louder and marketing the same product
Pretending decline isn't happening
Claiming something is still good because it used to be is a risk. You either fix it properly with a clear deadline, or shut it down and move on. Dragging it out only wastes people's time.
Something that can bind people together is a clear vision. Clearly explain how LS-RP's SAMP future can beat RageMP. If that's not clear, then people won't stay. Either produce a believable roadmap that gives players a real reason to choose here over there, or accept the answer the market has already given and step aside.
I've got nothing but love for this server and community, I hope the management team gather the feedback and figure it out.