So after reviewing the following resources I can't find anything specific about the removal of that button but my knowledge of the architecture of bitcoin core is limited and it may be a change documented here necessarily implies its removal:

https://bitcoin.org/en/release/v0.17.0

https://bitcoinmagazine.com/articles/bitcoin-core-0170-released-heres-whats-new/

I did learn I can just leave all those fields blank to effectively do the same thing as the New button in Receiving Addresses used to do