As stated earlier, I am totally fine and understand the Steve pick but here is the controversy right now that I think people have with the character:
Steve comes from a low-budget, low-quality series that turned into a massive hit. It isn't your traditional platforming gaming series but is rather more like Angry Birds, Fortnite, etc. It represents the divide and changes in the video fame series. You have people that prefer high quality console games that appear on Microsoft, Nintendo, and Sony consoles as well as PCs and then you have these games slew of games that started free for play on online websites or as phone apps that have taken off and are now more popular than the console games due to accessibility.
This shows the divide in Smash fanbase. Most fans, especially older generations, want to stick with classic platform characters like Crash, etc. However, those characters are not as well known in the mainstream market or by younger generations. I personally think MasterChief is bigger than Steve but I maybe totally wrong when you look at sells, etc. MasterChief comes from a higher quality franchise with tons of fan support in the West but isn't universally popular like Steve. My generation will likely scoff at the Steve pick but overall it was a good decision. Btw, I loved MissClickGamers response. I watched her, Aaronitmer, and PapaGenos responses. PapaGenos was who I went with live.