Not trying to start a dog fight on the topic. I have been in both as well. Not even sure why it is an issue. All cruise ships and lines have way more in common that differences. Just wanted to reply to a couple of your points and then I will move on. First, the reason that the food is the same is because Carnival WANTS it to be same. She now is a Carnival ship. The Italian flair is way more about the heritage and decor than food (which BTW is way better than Costa food).
In regards to the kids and keeping them happier on Oasis (class), it really depends on ages and demand. I would def concede the flow rider, but the rest not so much. A merry go round and flow rider attract a WAY different crowd. I s the ice rink open every day? I do not believe so. Saw WAY more adults on rock climbing walls than kids. I could go on, but will not. No need. I did a lengthy review of our sailing on Oasis and posted it on the RCCL main page as well as here. There is a reason we have only sailed Oasis class once.
Listen I get the hype, the wow, the sizzle (Icon right now). That comes with some caveats, no tender ports (NONE) and limited ports of calls. For a lot, the sizzle wins….not for us. Your opinion (or your kids) may vary. Time to move on.