The thing with Zestiria is that it is just more of the same (perhaps a little less competent than usual) in a series that is desperate for more exciting plots, scores and battle systems.
Weirdly enough, I think ToZ have a lot of new systems that shake things up (regardless of how sucessful they are) to make me think it is "more of the same" gameplay wise.
The plot felt really different from usual Tales of. I think that keeping the medieval fantasy focus all the way through in a landscape of JRPG that thow extange technology in with the fantasy setting or that are straight-up futuristic or based on reality makes it feel bolder and more unique right now. I was a thowback to older times in the genre I appreciate.
The plot also is very different from most Tales, getting rid of fluff and typical elements like like romatic interest subplots, treason among the party, racial undertones, duality of worlds among others. Throws many things that have been a staple in many the serie's plots and delivers something more simple plot that along with the other elemnts reminds me more of Dragon Quest than Tales. Given how few DQ releases tend to be over here I really value that.
I also like the strong directoion Zestirias has and how the scenario is reflected on the battle mecanics. It makes it feel more soild and inmersive and that has value.
That's not saying the plot is as good as any DQ or that it doesn't have issues - it has a lot and the DLC is terrible. But there is stuff that is very cool and enjoyable about it.
While Zestiria isn't necessarily worse than the other games, it most certainly crossed the line at which it should've brought more to the table than it did. It's the textbook definition of bland.
From my point of view I don't think it had to do more. One of the things I like of it as well is that is very ambitious and the people behind hit were clearly very passionate about it. The issue is, as many pointed out -is no secrett- polish and wrapping up. If Namco had given the team 6 more months I'm sure most people's opinion on this game would be very different as it would be the game itself. Namco could have perfectly have done this -the actual anniversary was still quite distant at the time of the japanese release after all- but sadly the pulisher keeps not giving the people in charge of making the games enough resources to complete their vision in all areas.