Do you have any evidence for this claim?

I gave you four different souces that you revoked as 'GAME FREAK LIED, I JUST CAN'T PROVE IT'.

Similarly, given the presence of cleary reused assets regarding animations even in overworld models like characters, one might wonder where the new content is.

I'll quote what someone else said on the topic:

A technical aspect reason why Game Freak can't reuse animations from 3DS is due to hardware and technical reasons. The 3DS's hardware is completely different from the Switch's hardware which is pretty obvious. Copying and Pasting animations from one hardware generation to another isn't practical because a lot of the old code made to parse and render stuff were built around the assumptions of what the old hardware was capable of. This means that the engineers and animators have to figure out what can be transferred over and what doesn't. And for the stuff that can't transfer over, the animators would have to fix or recreate the animations from scratch. Hardware changes is one of the reasons why porting old games to newer consoles and computers tend to be really difficult, because a lot of the old code weren't made for the newer hardware. Think of it like plugging a VCR into a modern HDTV. Sure you can try but it may or may not work because VCRs weren't specifically made for modern TVs

DexNav

No such interview seems to exist.

Realistically there are multiple reasons for a feature to be dropped.

Reason 1 - Feature bloat: Everything from the previous added onto whatever new is added would be rather ridiculous specifically when looking at reason 2

Reason 2 - Hardware constraints and time limitation: Sometimes developers look into a feature in previous games, let's say seasons from Pokémon Black/White and realize that it wouldn't work properly in the new game and sometimes publisher/developers do the math and find out that focusing development time adding previous features to the newest title wouldn't be feasible with everything new being added as well and if that isn't the reason then reason 3 usually is.

Reason 3 - Feedback: Sometimes features don't 'click' with the majority of the consumer base to which developers take that feedback and put the development focus elsewhere instead.

If Game Freak added every previous feature in the newest game, the game would be a costly bloated mess. Developers have to decide which features are worth maintaining, old features might not make the cut because a new feature makes it irrelevant, or maybe because it's not popular enough, or there's some technical or game-play reason why it's difficult to keep alongside a new feature.

Hope this helps.

Masuda was referring to quality as in over quantity AKA overall game balance, not specifically Pokémon balance.