I noticed you and Andrew seem to be talking past each other here. Andrew is talking about Wesnoth in player vs player mode. You seem to be talking about the scenarios. From a balance perspective these are two completely different games.

For anyone reading here who hasn't tried both modes, the PvP mode is a fairly good and balanced standard wargame. You can play against the AI, which is decent but not great, or against other players online.

The scenarios on the other hand... what everyone is complaining about is true. But this is a problem with the scenarios, not with the game. In order to make them "interesting", pretty much every scenario has a bunch of gotchas in it, like if the objective is to get your general to the other side of the board in 25 turns, on turn 10 some event will happen like a dam breaking and blocking off the main path or a new enemy appearing on your flank. On a first time play through, it is very hard to anticipate what gotcha will appear and how to mitigate it. To make it worse, most scenarios are ten or more battles long, and you need enough survivors and gold from the early battles to win the later ones. So, if you barely win an early battle you've basically lost the scenario, but you won't find that out until later.

To sum up, when people are loving on Wesnoth, they are talking about the game, and mostly play it in PvP. When people are hating on Wesnoth, they are talking about the scenarios, which are truly unbalanced. Tell people to try the PvP first.