I don't like the framing as "TH" being the radical outlier and "Engage" being the traditional one.
The characterdesign of engage for me was at least as far removed as TH from classic FE, in my book even further, and the rings with calling old heroes felt more FE heroes inspired then any of the old games and felt overly fan service focused. People never played FE JUST for the gameplay, and while the gameplay might have been closer to old FE (still haven't gotten to it...), the packaging was feeling alien to a part of the fan base.
TH had also the luck to come out into a market that was more inclined to political drama in their fantasy story thanks to GoT I guess.