Game Freak created the perfect pokemon and waifumon at the same time when they made Ivysaur. She's beautiful, caring, intelligent, protective, strong, and a bit of a tsundere. No other pokemon can compare.
You see, Ivysaur doesn't need daily marketing and coom spam everyday to be relevant. The design sells itself because it's unique, original and clever.
It has bits of toads, dinosaurs and cats which attracted many different kind of fans, while the waifumons we see in recent games are just just generic template designs trying too hard to be Gardevoir and Lucario, no originality.
The Whole competition are just lazy mimics that the market is over flooded with.
Ivysaur however tested the times, proved to be a successful and iconic formula of several species that made it win its own games, a place in Smash among the video games giants, and its modest cult following that doesn't need to open up 50 threads per day just to not let people forget that it exists. Fursona waifus are just marketing stunts that always gets forgotten and replaced whenever a new toy gets released, while Ivysaur with Its influence, significance, and popularity is eternal.