I do agree with the conclusion but i dont so much agree with the "light" term, as i think you mean light as in not as dark as persona 5, but it can be interpreted as light, slim on features, wich i dont think it is.
With that said, the Devil survivor games also look pretty light at glance and they are very dark.

I do expect it to be a Devil survivor like game, but instead of there beeing a doomed world, you have a Fire emblem world you can go to, with the added twist that you can come back to reality Persona style. Either way, i think this game has alot of potencial and i'm glad it became its own thing rather than a simple cross-over. It just looks like a SMT game with some FE inspiration.

Right.

Reception is more positive than anything else. There are negative and mixed reception, but the majority is positive.

I only said "It could've" just as an example that we do not know much about SMT x FE, and in that trailer we barely saw the fantasy world that the devs are talking about, and it isn't going to look modern as I've even provided a screenshot of what is the exact opposite. Until we see more of this "fantasy world", we cannot say that the game is not being loyal to its announcement trailer.

And I don't see how the trailer implied that that's the only way you will be playing the game, again, even if you feel that way, we do not know how it will play out.

I agree with some of the things you said, and i do agree that the term "light might mean that, though I do mean physically lighter :P

But I also think there will be two worlds that you can access seamlessly, and I think the FE world will be more of what people wanted, but I think that the Persona-like world shown in the trailer is welcome and i'm interested to see what they will do with it.

I'm pretty sure we did. The battle arena they are in is surrounded by an audience that isn't human. That's likely the "fantasy world" he was talking about, as it's clearly not the human world. The screenshot you showed just looks like a shrine at a park. There are plenty of places in modern Japan that could look like that.

I don't see how it doesn't. It's literally showing gameplay from the middle of the game. The character are seen to wear different outfits, and the outfits bring worn in the middle of the game sections, are the same ones being worn in the majority othe the "slice of life" gameplay being shown. Obviously there's more to see, but I can't see how anyone can genuinely try to argue that this trailer isn't majorly encompasing of the whole game. Literally the only thing that might not be is the song, because it's done in a typical OST style that doesn't always reflect the overall musical score of the related game or anime.

But seeing as we literally see a main character singing on a stage in a typical idol outfit, I don't think it's a stretch to expect that in the game either.