The difference with Birdo/Toadette here is that (and working with the specific characters, not the species) Birdo prefers to be referred to as a girl... and is referred to as a girl. There's one mention of her being biologically a boy, but in all instances Birdo is referred to by her preferred gender. Why should a character who has always been referred to as a girl suddenly become genderless?
I'm not arguing that toads should have explicit reproductive parts, or anything like that. All I'm saying is that Toadette wears dresses, has pigtails, and has been called a "she" since her inception. By removing that, we are literally taking away part of Toadette's identity. They could even create a new gender-fluid toad-species character, but Toadette already identifies as a gender.
I'm not arguing that toads should have explicit reproductive parts, or anything like that. All I'm saying is that Toadette wears dresses, has pigtails, and has been called a "she" since her inception. By removing that, we are literally taking away part of Toadette's identity. They could even create a new gender-fluid toad-species character, but Toadette already identifies as a gender.