Adding a simplier design with functional code is a good thing. If there is a mid level developer that can't follow the current state of the art, than he is not a good mid level developers. Also "good" junior developers have mostly zero problems in understanding more functional code. I mean you don't need to understand Applicative Functors to use map/flatMap.

I mean there is a line which you should not cross too fast when introducing functional stuff, however most people just don't even try to understand the simple stuff even that it is way more simple than most while/for loops.

It should also be mentioned that responses similar to the examples have approx. no substance, detract from the quality of the conversation, provides no value to the team, and will likely only decrease mutual trust and respect.

The only consolation is that the system in question hasn't entered production yet, and probably won't for at least a year at the rate it's progressing.