Civ5 started terrible and stayed pretty bad, managing to fix some of the problems that should have been caught in the first game's development. The solution in Civ5 was to try and fix some of the blatant balance issues, but some things were doomed by a flawed design philosophy. BE, from the start, hasn't really fixed balance but patched over balance issues with new systems, ignorant of the underlying flaw. A flaw which could easily be fixed is the brokenness of trade routes, caused by the ass-backwards way TR gains are calculated, but instead of fixing the yields on trade routes, BE vanilla first merely capped TRs by population, and RT added a bunch of crap that doesn't address anything about why TRs break the game.
Definitely agreed on the AI playing to lose - that sort of thing is exactly what a decent 4X should try to avoid, and RT made it 10x worse if not moreso. AFAIK that is the sort of thing people who don't know good game design suggest on forums.
There is definitely something to say about a developer knowing when to ignore the fanbase and think about what makes a game good and interesting to play. I think the problem runs deeper that blaming the novice lead developer, but being pulled in multiple directions and something wrong with design philosophy in the past 5 years or so.
Maybe I should put my money where my mouth is, learn how to deal with Civ5 modding, and just try to make the game into something that is remotely playable. Unfortunately, the attitude of many people on this forum discourages me.