"Might vs. Magic"

No, you didn't claim that Nagas are inferior in any way, but you did state:

This is more of a problem of good "feeding" rather than the weakness of Nagas.

This is specifically a problem with Nagas, or rather, with their inability to retaliate effectively. Dragons love to attack units with special abilities – Nagas, Vampires, Pit Lords, etc.

In other words, equally strong stacks of Nagas and Knights have different chances of getting the first strike from dragons.

Of course, if you compare a Tower with a Rampart or a Dungeon, it is inferior. But I said that the Tower can compete with a Castle and a Swamp.

The same applies to a Castle and a Swamp. For the Castle, the Marksman + Knights combination is clearly stronger and easier to manage, plus Angels in the long run. And the Swamp has a very balanced growth and excellent heroes. Both of these castles are clearly stronger than the Tower in both Shades of Darkness and The Restoration of Erathia.