Except that TMs never broke the power curve of the game. It is the time honored comparison between someone who was adaptable, but fragile, against someone who was reliable, but less reactive. TMs had good burst potential, but if they ever got caught in a fight (in the Matrix or the Meat) they were hosed. And how many runs go by without any fighting? People only looked at "OMG THEY CAN GET RATING 12 PROGRAMS", and promptly pissed themselves in either terror or minmaxing glee, without looking at the whole picture. It is as bad as looking at a D&D character by their effectiveness in a single arena battle, instead of what they do in a dungeon crawl.
Did you recall that book in question? They were amazing combatants able to generating very large pools for any skill on demand. Threading + Skillwires go look it up.
But I agree that amount of nerf we are seeing in 5th is way overboard. They made a lot of low level fixes for them (Like the smartlink complex form), and those should have been kept around, or at-least re-instated by now for love of the game.
Threading and Skillwires was a decent combo, but one that took multiple submersions to be any use, since the rating of your biowires were equal to your Submersion rating. You're talking about something you can't do out of the gate, and requires a shit ton of Karma to set up. That's like complaining that a Mage with four Initiations all geared to one thing is more powerful than a straight out of chargen character. After more than a couple dozen karma, you're expected to be more powerful.
But even that is part of what I'm talking about with their burst potential. You could boost things with Threading, but you had to resist Fading, and the higher the new rating, the higher the Fading, which you took directly to your brain. A single bad roll on that could fuck you up for the whole run, much like what happens when a mage overcasts their spells. You can get kick-ass results, if it works. It wasn't reliable or safe, and was basically getting on both knees and begging Murphy to come down and screw with you.
Like I said, it is the difference between a glass cannon and swiss watch. The glass cannon can do a lot of damage, but it is easy to take them out. The watch, on the other hand, is more limited in what it can do, but it can do it all day long, and will take a licking and keep on ticking.
Adaptability vs. Reliability.