Star Trek was wildly popular back in the 80s and 90s - things were not exactly rosey then, especially in the UK - yet the message that things could be different and humans better resonated for decades and decades.
How does promising a rosy future help people who are dealing with s%&# TODAY?
The problem with placing something in the far off future is that it risks being seen as irrelevant TODAY (I dont like TNG for that reason. I just couldn't relate to the characters.)