Shogun 2 and older games massively lose out on the UX. Especially in combat, the games have much less quality of life.

Furthermore, the newer games simply work towards a somewhat different audience. The studio has clearly picked up on the success of Warhammer and after stumbling both through all of Three Kingdoms and the launch of Troy, they seem to have firmly settled towards the more fantasy direction which is counter to the philosophy of the earlier games.

While I certainly support trying out the older titles too, calling Troy a simply worse game than the older titles is a bit reductionistic and definitely has a personal bias and may be somewhat misleading, even if your advice was in good faith.