In my opinion, the imbalance is more due to specific heroes rather than the race itself (certain heroes dominate on small maps), and also to a large extent, it's down to random chance. Regarding the late game and rushing, I'll reiterate that on most maps, it's not necessary to wait for months, but rather to utilize your strengths. Waiting for a Knight to level up 100 Paladins is already a passive approach.
And tactics really do matter. With the right strategy, you can defeat opponents with significantly superior forces. By the way, I'd like to suggest trying out duels. In a dozen games against a strong opponent, you can learn a lot about tactics.
As for the sixth installment, honestly, I'm not too concerned about how characters look. What's more important to me is balance, and it would be nice to have more alternative upgrades for creatures and to add around 20 skills (instead of 12). All this would add variety to the possible tactics.