Thats interesting, because my experience is the opposite. I play a sixth level Cleric/ MC Fighter in a weekly 4e game, and have been slogging through hundreds of feats and powers and Paragon Paths in the Compendium to try to figure out which combinations will synergize best through Paragon Tier. The combinations are endless, and although any combination will work, I hate feeling like I'm missing some better feat/power interplay that would make the character--not optimal--but truly useful to the group.
The retraining mechanic is a wonderful addition/reimagining in 4E. The options in 3E were seemingly far more, and flexibility when noticed was far less. Now one can explore different options to see how they work in actual play yet may still dump them when they don't perform as well in tier or in general.
Example: My first Assault Swordmage. Even the at-wills have numerous options, yes, but retraining was a Godsend. On paper, Lightning Lure really looked like junk, so I all but ignored it. Then in play I began to see where it would have been extremely useful. I retrained in to it and found it far better than I had ever imagined so long as I was thinking and using it creatively. Without that mechanic, I could easily have missed out on the best at-will in the game. Simply crunching a few numbers simply did not give me the initial data needed to make a truly informed decision on the usefulness of the power.
The stat boost mechanic also opens up a number of options. If one straight mins/maxs one's primary/secondary stats and essentially dump the rest, then one loses a little flexibility too but one can alleviate it somewhat with the boosts as one progresses.
That doesn't mean it takes less thought, it just alleviates the need for anal-retentive analysis at character creation.