My big issue with Shadowrun was always the initiative system making speed OP, and diving into either the decking or astral plane makes the rest of the players twiddle their thumbs for 20-30 minutes.
You are definitely correct about the speed problem, but the rest isn't really an issue.
In SR, you play a team of runners, a group of highly specialized individuals - if you run properly, you'll only rarely be in the same place or situation. It just doesn't make sense to have the infiltration expert, tank, face, mage, etc. all in one spot. Not during a run, anyway.
This ain't D&D where everyone is always moving in one big blob through a linear corridor. Everyone generally fulfills their role independent of the others and therefore you always have the focus on one player, then the next, etc.
That's just in the nature of the setting. So deckers/mages doing their thing while the others are doing nothing is no different from any other role doing their thing while others are doing nothing.
This is also often just a DM problem. Our group always gave "inactive" players something to do, like playing an NPC, etc.
Also adds a lot of fun to the table, as it gives every player the opportunity to throw a few wrenches in their own plan (which players actually like doing, go figure).
Frankly - Shadowrun was always a game which was popular IN SPITE OF the mechanics because of the setting being a load of fun. The one good thing I'll say about the mechanics is that they're dripping with flavor and really fit the vibe that they're going for. Unfortunately, they're also clunky, hard to use, and badly balanced. *shrug*
Frankly, if anyone thinks SR rules are hard to use, I question their competence at the table. I mean, yeah, the decking/hacking stuff is rather complicated, but that's also something you can simply play without (did that for almost 10 years, works perfectly).
But the rest is anywhere but clunky and hard to use.
It has the right amount of crunch and detail to actually be considered a game that isn't just "my first RPG experience" ala D&D5E, while not going overboard with details like The Dark Eye does (trying to summon a spirit as a shaman of the southern lands scarred me for life, had to cross-reference 4!!!! books to get the full rules, the process took 1 hour).
Besides, throwing a huge bunch of small dice is just very satisfying.
Badly balanced is true, and that does require some houseruling, though I don't think any SR edition (except 6th) requires tons of that.
The DM saying "If you use it, I will" generally solves all vastly overpowered problems (e.g. mass-summoning spirits, triple initiative phases, etc.).