“Wow, this one thing from this one game is really cool, maybe we should take inspiration from it and try to incorporate it into our game?”
“Nah, can’t do that. It would be stealing.”
People constantly mistake inspiration for theft and it shows when people get so rabid over the defense of their favorite MMOs. Did Blizzard “take” ideas from Guild Wars 2’s mount system and incorporate it into their game? Yes.
Does Dragonriding function the same way Skyscales and Griffons function in GW2? No, and I can tell you this as someone who has played GW2 since launch and grinded out the requirements for obtaining Skyscales and Griffons (Firebrand mains rise up.)
Creativity comes from recognizing the genius of good ideas of predecessors and then building upon it.
Easy example: Paladins in Warcraft would not exist if they did not take inspiration from previous fantasy, namely old school D&D. But guess what - the original paladin from D&D was based on the novel Three Hearts and Three Lions, and that book is based on the original Carolingian Cycle.