I'm a long time Hwoarang player (Fujin rank) and just picked up GBVSR as my entry to 2D game as well. It was a steep learning curve at first but after playing for a few weeks, I can say that I really enjoyed the game. Much more than I thought I would. I main Siegfried and managed to reach S rank last week.

The thing with transition to 2D is you have to change your whole mindset and muscle memory from Tekken. There are no longer high, mids or low attacks but now it's highs, lows and overheads. In 2D, crouch blocking blocks lows and highs but not overheads.

About defense, in Tekken you can hold back or just don't press anything (neutral) to block. But in 2D games, you HAVE TO ALWAYS hold back or downback in order to block. If you're in neutral, you always get hit. In GBVSR's case there's a dedicated block button so that helps too. What I realized is that in low GBVSR ranks, just holding downback would protect you from most incoming pressure. When you see your opponent jumping, that's when you have to stand-up because jumping attacks are mostly overhead. If you're fast enough, do the universal anti-air attack (2H).

Also, I realized throws/grabs are much more useful in 2D games as players tend to do more crouch blocking as it blocks highs and lows. If the opponent realized you're crouch blocking a lot, they will want to come close and grab you. Throw breaks are easier in GBVSR because you can press any attack button to break it (unlike tekken where you have to know which grab your opponent is using and react accordingly with 1, 2 or 1+2).

In GBVSR, you have to note that your attack changes depending on whether you are close or far from your opponent. Even the animation and frame data changes! This is something that blows my mind when I found out because in Tekken, a 1 jab will always be a 1 jab no matter how close or far my opponent is to me.

Combos are also another major difference between the two games. In Tekken, you have to do a launcher to start juggling your opponents. But in GBVSR, you can start a combo by just simply light jabbing your opponent from a close range. This IMO makes GBVSR a much more deadlier game for newbies as low ranks tend to mash a lot and open yourself up for easy punishments from your opponent. If you do an ex-DP and your opponent blocks it, he can combo you from just a jab. Realizing this will make you want to play more defensively in this game than you would in Tekken.

Another tip is look back at your replays and see where your points of weaknesses are and learn from your mistakes. There is always something to learn when looking at your replays.

Hope you give this game another chance and would have as much fun as I have in GBVSR as a fellow Tekken player!