TMIT, I'm curious about why you think medieval warfare is bad. I agree, though I've never been able to pinpoint just why. Despite that feeling, there have been many times when I've just had to grit my teeth and gather up the trebs/knights/pikes/longbows and go for it. Interested to hear your viewpoint.
1. Bombardment takes longer than any other era by far
2. There are no mid game + production boosters like kremlin, caste/guild/chem/sp workshops, factories, drafting, etc
3. If you DON'T bombard, you once again fight the highest defensive % bonuses in the game.
4. The AI prioritizes medieval techs, making the liberalism line more attractive for trade value (you have functionally several times the research speed just by avoiding the medieval techs and trading for them, but if you do that any medieval attack is delayed)
5. There's not enough time or EP buildings to accrue much spy help
6. On high levels, the AI can SPAM units, and with all that bombardment time, you'll be forced to kill more units, eat more WW, etc even if you DON'T lose units to RNG screw
7. With longer-lasting wars, you risk the broken, garbage, joke mechanic known as vassal states kicking in against you.
It's not like it isn't doable, but it is one of the more dangerous eras to war and also among the most situational; even in situations where it will work earlier or later war often is a better deal.