SFIV in general has a very different timing on everything, not just combos. The new gen of people never played the other stuff and thus I think they might find it easier to learn. Us old dogs have to re-adjust to it, it's a learning curve but it's worth doing.
I started playing SFIV with Abel and Crimson Viper but I was getting floored, then when the Super update came out I started playing with DeeJay, also got floored, it wasn't until Arcade Edition that I found a better balance in my game, playing online helps tremendously and getting beaten is part of the process.
You may think you're a decent fighter in all of the other games but you've never had access to the different array of levels you find online, not even at a real arcade during the heyday would you be able to find so much top talent. Is this safety bubble people have been dealing with for years playing their thing either at home or at an arcade with people about their same level, you just never grow, now here we are in this day and age where everyone has access to play this games with one another and the real contenders just come from everywhere.
I could guarantee you that if you play some of the older games online you'll be right at the same level you are in SFIV.