Except that TMs aren't pallet-swapped Mages for the digital world! They never were supposed to be! They were the 'Swiss Army Knives of the Matrix'! Don't compare them to mages, compare them to Deckers and Riggers.
In 4E, a TM was a glass cannon. You had high burst-power, with threading high-level complex forms, and could adapt to situations on the fly, but since you took all Matrix damage and Fading from your Threading and Compiling straight to your brain, you could get yourself wrecked. Plus, any of your abilities in the meat would be, shall we say, sub-par, since you didn't have any access to realspace initiative boosters until you had at least two submersions under your belt, so you were looking at only a single pass in the meat-world, which severely limited your ability to help the team if combat started, unless you were a TM Rigger. And yeah, TMs could be riggers from start, without having to drop submersions on it. They were actually pretty good at it, too, and there was an entire stream devoted to it.
On the flip side, Hackers and Riggers were more reliable. Yes, they didn't have the ability to adapt on the fly in the Matrix like a TM did, but they could take more abuse, and were less likely to get themselves crippled for the rest of the run by botching a roll early on and taking half their matrix condition bar in damage trying to send an agent to do something for them. More importantly, because they weren't as Essence-dependent as TMs were, they could get ware that helped them be more of a threat in the meat, as well. Even if it was just first-level Wired Reflexes, that kind of thing makes a big difference when you're in a firefight and avoiding a severe case of lead poisoning in the Barrens trumps doing matrix searches to find out who sent these gangers to kill your team.
Fast forward to 5E, and TMs got raped up the ass by a troll with a sandpaper condom. That's really the most politely I can put it. The balance between adaptability and reliability is gone. Deckers and Riggers are both more adaptable than TMs, able to shift their attributes around on the fly, and load up different programs to suit the situation as they see fit, and they remain more reliable, still being able to take more abuse, and being able to do more in the meat as well as doing more in the Matrix. TMs keep all their old disadvantages, lose their adaptability, lose access to the Rigging aspect entirely unless they drop Submersions on it, and the fact that they can't form a PAN means they can't even secure their own damn gear, much less help their team on matrix defense. A TM who actually submerges and gets to Rig won't be able to actually control multiple drones like a Rigger with their RCC, and can't secure their own drones unless they're jumped in. And because you can no longer hack from the secure van, or some other safe space, the weaknesses when they are in the meat are even more pronounced.
The only path that produces results anywhere close to what a Decker or Rigger can do is if you play a TM as a pet class, go all in on Compiling, and have your Sprites do everything for you.
So yes, the archetype really did get that rotten in 5E.