On emperor and below this still is a rather theoretical discussion for ancient and classical - If not Tamar, I rarely see walls on these levels... So Archer rush might still be alive and kicking...
Immortal and Deity is a different thing but nevertheless walls have been too easy to get over IMO.
Personally I think it's a good move in general - It WILL make it harder for AI to conquer cities but they are not very good at it right now either. Will help them being around longer therefore giving them a chance to evolve...
Walls only benefit the human player. Making them stronger only makes the game easier for human players, although might help city states survive a touch longer.
I think the combat system has all the pieces right, it just needs to rebalance them.
Fundamentally, battering rams need to be nerfed, and Seige need to be resistant to ranged attacks. I think the best solution for rams would be that they lose the %damage to wall affect completely, and instead just give the linked unit +5 or +10 v district defences. That way, hitting walls with Melee would hurt - as it should. Seige should then get +5 or +10 defence v ranged if they haven’t moved that turn - they need something, because Seige just gets chewed up by district defences currently.
After that, you just need a few minor tweaks. Make Anti-Cav cheaper, and maybe buff them v melee and ranged in specific situations (eg fortified on a hill); make Knights harder to access and build (that’s hopefully happening in GS); nerf Light Cav against cities (eg -17 v cities).
After all that, you might then look at maybe improving the value of Forts and walls a little. Like maybe Forts give +0.5 housing, and walls buff adjacent farms. Maybe ranged have ZOC if garrisoned in fort. Maybe you get +1 loyalty for each unit garrisoned in a fort, in addition to any loyalty for a garrisoned unit in your city centre (that’s probably too strong).
Whatever. But nothing is going to improve unless battering rams get nerfed and seige are more resistant to ranged attacks.
...and also the AI gets better... but that’s a whole other thing...