Civ 5 is not a dumbed down version of Civ 4. It's different.
From a strategy perspective, I vote that Civ 5 requires me to be more disciplined than in Civ 4.
Civ 5 requires me to weigh how to specialize my cities and how to use finite resources. It requires me to think about what resources I want, and how defensible my city placement is. It requires me to deploy units as a real military advisor would. Every choice I make seems to be an important one.
In Civ 4, I can dominate the game simply by having bronze or iron, when my neighbor has none, and then spam the strongest military units. In Civ 4, I can build cities chessboard style, for no reason other than to set them on auto-build, and add a few coins to my coffer. In Civ 4 I can build a stack of units a hundred feet high. In Civ 4 SODs always attack with its best unit, and defends with its best unit.
In Civ 4, I never bothered to make paratroopers, marines, or blimps. There are too few scenarios to require a unit with the territory penetration of paratroopers. Marines can't upgrade to mechs and amphibious assaults are rarely useful. Blimps never seemed to do enough damage, and spies were more useful for scouting and damaging improvements.
Only played Civ 5 once, and suddenly paratroopers make sense, because I needed to overcome a 2 hex choke-point.
I don't see lack of religion to be a problem. Vanilla Civ 4 didn't have them, and there were few strategic reasons to not use religion. If you could found a religion with your first research, you might as well for the +1 happiness. Then every other Civ wanted you to open borders with them, giving you the opportunity to scope out their map, and spread your religion all over the place. Pop a great prophet, and now you're getting gold on top of the huge early game bonus.
Strategy implies choice. If founding a religion is almost always the best move for a Civ that starts with mysticism, then I would say it isn't much of a strategy.
Espionage is something I really miss from Civ 4, as I miss the Diplomats from previous Civ (2 or 3?).
I think Civ 5 has better baseline game concepts, and will provide more opportunities to be expanded on or exploited by a future addons than previous versions of the game. So I'm hopeful that I'll be playing Civ 5 for many years to come.