Your comparison with chess shows the problem with Civ5. Chess is a tactics game. Civilization is a strategy games series, of which Civ4 is a fantastic incarnation. Civ5 is what happens if someone who likes Panzer General too much tries to shoehorn its inherently tactics-oriented premise into a strategy game.
Civ5 has a lot of design problems, some of which have been addressed by G&K, others haven't (like the atrocious AI). But that's not the problem. The problem is that Civ5's premise is inherently flawed and there's no amount of addons that could fix this.
Frankly, I think if there's anything in Civ5 that's better than in Civ4, it's more worthwhile to implement it in Civ4 than to switch to Civ5. I for one am fairly certain that thanks to the C&C community Civ4 will outlive Civ5.