The fighting game genre never died though, Capcom fighters died. Tekken and Soul Calibur were huge during the PS2 gen, Mortal Kombat in its shitty 3D format was huge. Street Fighter IV revitalized Capcom's role with competitive fighting games mostly.
"Newcomer friendly" is a pretty empty term. More tutorials on how to zone opponents out, outspace your opponents, anti airing jump ins, playing defense, dashing instead of jumping, that would help a lot of newcomers. Mechanically, making the execution less strenuous helps out everyone, it isn't catered to newcomers specifically. Someone with experience can play as multiple characters much easier now, since optimal damage combos are easier to nail.
You'd have to elaborate on the decline in fighting games at one point, as they never really went away like, lets say, JRPGs did on consoles. Competitively, fighting games only got bigger as more time went by. It wasn't like fighting game locals and tournies dramatically decreased from 2001 to 2006.
I'd also add some pros play fighting games strictly to win cash. Justin Wong is competing in multiple games right now, dude doesn't care how big each community is or if casuals are having fun.
