Celebrating and taking pride in what has been achieved is part of what motivates people to defend it. Doomposting online does nothing to motivate people and merely depresses them.
Every inch of progress has been won through a combination of a rhetoric of hope for what could be achieved, and a recognition of the shortcomings of the current system. Having the former without the latter leads to complacency, but having the latter without the former leads to apathy and despair.