I think the grimness and gloom are part of its identity. They always have been. The writers often exaggerate, give shock value and ultimately hollow stunts the front row seats, which is when it becomes too much.
It would be nice to see this show change and really represent what's going on in East End, at least a bit, but you would have to be quite a master to pull it off. Once in a lifetime kind of talent. So that can be scratched, it just won't work. People expect that "grittiness" – although I every time I see that noun – and too much of a change would drive them away.
As you rightly point out, if only they put a little more heart and honesty, things would be much better.
But even at its absolute worst, I love this show. Some of the episodes in those dreary periods are just pure magic. When it's good, the magical episodes are a staple. The show always had a kind of tightness to it and some its writers know drama and what a good script is.
Corrie has been overrated for a long time now, I really hope it gets better soon, but in the meantime, EastEnders should really be no. 1.
Those 20m viewers peaks EE achieved, even though they happened in 2001, seem like a distant memory. Perhaps never again.