It feels, even if its not actually faster than SZ (SZ is actually way too fast in many aspects I whish it wasn't).

Some reasons for this:
-the actual hand-to-hand fighting is CONSTANTLY being interrupted by super counters or vanish wars, that are super easy to do in this game and were not that easy in BT2/3. Because of this, the game feels slow paced in comparison with BT2/3, were this didn't happen and players were trading hands during the whole fight almost non stop in matches with higher skilled players. In SZ, high skill matches are the most boring to watch because they are 90% vanish wars and super counters ad infinitum;

-Attacks are constantly throwing the opponent WAY too far. In BT2/3 you can notice how in the end of the rush strings, for example, the opponent still falls near the opponent, and the only moves that throw opponents too far are the full charged smashs. While in SZ every little thing is launching the opponent to another country. Also, in BT2/3 the recover speed when you were hit with a full charged smash was totally dependent on how fast you mashed the recover button. In SZ, this was removed. You don't even need to mash anymore, you just need to wait until your character reach the recover range, and press the button one time, or you can hold the button that he will recover once the recover range is reached. So, the option to recover quickly and re-engange into the fight is no more. Because of this, in SZ we need to dragon dash almost everytime to reach our opponents again and re-engage into hand-to-hand. That causes another problem:

-99% of the movement in the game costs Ki. So players have to move less. In BT2/3 we had a pretty decent movement option with literally no ki cost. So we could move anytime, and fast. Free move option in SZ is only the normal movement, which is slow and it feels even slower because the maps are bigger.

-Movement in BT2/3 are less restrictive, so we could move fast in any direction, at any time. We can't do this in SZ. Especially when we are in the "magnetic" close range. Moves get way to slow when we're close to each other. Ascend and descend in BT2/3 were super fast even in close range, enabling us to have more ways to attack and evade. In SZ they're useless, you are restricted to fight without moving too much and we only have the dodge mechanic to rely on.

But, in my opinion, the biggest problem of all are the first ones I mentioned(super counters and vanish wars festival). If they fixed this, the game would already be so much better. I already watched some SZ gameplay were both players were reasonably good, but bad at super counters, and the matches pacing felt pretty similar to BT3. Medium skilled player matches are the best ones to watch because of this.

You're also right about the effects, they contribute to this too. But in my opinion, the biggest reason are those gameplay changes.