You take a mon like Floatzel and you look at what their intended role on a team is. Fast physical water type that can also have boosted speed in Rain. We have Barraskewda in SnS so it's "ok" to cut Floatzel (it's not but w/ever). You check and make sure that they have a similar BST spread that also allows them to do their job so they're somewhat interchangeable.
This reminds me of a similar experience of fan meltdown, although in this case it actually did (I'd argue unjustly) doom the game; Marvel vs Capcom Infinite.
During the development of the game, many people were awaiting the triumphant return of series favorite characters Wolverine, Magneto, Storm, and more. Things were very unclear at the time, because those characters were no longer owned by Marvel; Known as the X-Men, they were still a property of FOX, and would have to get their rights bought out for use in the game. The Devs likely knew early in development that the X-Men weren't able to be licensed, so they developed characters that played similar to the way their original counterparts did. A 'function' of the character if you will, with similar mechanics but different graphics, visuals, and context.
In an interview with the developers, to try to save face at requests for Magneto, they said that the 'function' was what was important, not the character; basically that Magneto is worthless, but their function isn't. This was met with tons of outrage.
Overall, that could argue for or against your point. On the one hand, Floatzel has a value as a function and as a character, each independent of each other. Replacing Floatzel with Barraskewda feels bad, because even thought the function is there the character isn't. But Barraskewda also has value. It's different to Floatzel in design in it's own ways, being a bit sillier looking, and there will certainly be people who end up preferring the newer take on a similar function. I feel like putting the effort into re-tweaking the function of creatures can only go so far when you also need to create entirely new characters and functions as often as Pokemon does. Besides, Floatzel isn't a character that would alone cause an outrage if removed. Besides all the Kanto staples and Lucario, I don't think any single character holds that much sway.