I think ToB is a great game, especially considering the price point. It is a bit low on replayability and there much less room for settlement customization compared to most other TW titles, but to be fair, there are lot of "fake" choices in Attilla. Managing food, unrest and squalor limits the customization, and one could argue that the main settlement customization in ToB has more choice than in Attilla and Warhammer.
For me the biggest disappointment of ToB is the battle AI: It's far below the usual level, and much more buggy than usual. The battles themselves are not buggy, and the units are snappy and consistent when reacting to orders (significantly better than Warhammer) and the pathfinding is also good. I suspect the release was rushed/forced, as indicated by the relatively late delay of the release date. I hope the team gets a bit of time to finish up the bugs and tweaks they couldn't get done in time for the release. With some post-release love, I think ToB will be a really good Total War, especially as an introduction to the series for new players.
The estates mechanic did not pan out well, in my opinion. It's busywork, there are no trade-offs / choices involved, and I think newbies will have trouble finding the Estates UI. But it also doesn't harm the game, and perhaps mods or post-release patches can improve upon it.
I think the harsh reviews are somewhat unfair, and perhaps represent the Total War community being disgruntled and unhappy for various unrelated reasons.