I disagree completely. I can't see any of this tech existing only 80 years after Nemesis.
Technology and science evolve exponentially for just 1 species... never mind for over 150 spacefaring FTL capable civilizations who share technology, science, knowledge and resources freely between each other (in late 24th century).
Voyager crew created a far more powerful/faster version of Slipstream in 4 months with limited resources. You cannot possibly tell me that the resources that Starfleet has in the Federation would be incapable of creating technology for synthesizing benamite crystals far faster, and prevent their degradation within 2 to 5 years (maybe 10) after Voyager returned and solve the phase variance issue.
You do realize using adaptive algorithms and AI in research and development in the real world has been a thing for a VERY long time and that it usually takes those algorithms at least 1000x less time to reach solutions compared to humans (on standard computer systems)?
In Trek, they have had the luxury of quantum computing in the 23rd century, and transluminal processing since 24th century (our quantum computer was apparently able to do 2.6 billion years worth of research in just 4 minutes).
Transwarp?
Voyager went through how many TW conduits and even had a functioning Borg TW coil (and detailed sensor scans of it).
Coaxial Warp? It worked... the crew adapted it to the shuttle (only for the writers to never mention the technology again) and even broke through the Transwarp threshold (Which admittedly did end up mutating Paris, but still... the data the shuttle accumulated and the biochemical changes Paris and Janeway underwent were well documented).
There are also Thermionic generators (which Voyager crew scanned and probably acquired from Species 8472 during their exchange of technologies), along with Tetrion reactor technology (of which Voyager had some scans from Caretakers array and also after studying the Subspace Catapult technology in order to help Tash repair it).
Seriously, even Quantum slipstream Version 1 didn't need benamite crystals but could only be used on Voyager for 1 hr due to quantum stresses to the hull. Seriously, with additional research, it would be likely dead simple to design a deflector system capable of dealing with the Quantum Stresses on existing or upcoming new Starfleet Ships.
And also, Starfleet encountered a solid Neutronium hull on the Planet killer in the 23rd century.
Studying that thing for 70 odd years would have produced ridiculous advancement in weapons, shields and hull material science alone which would even allow Starfleet to reproduce Neutronium in SOME quantities by late 24th century and merge it with existing materials as a composite already.
But no, the writers conveniently forgot about that.