I've scored almost 300 hours of network tv series, and a couple of dozen features, and 90% of the time it was all stock Logic plugins, with the following caveats:
• For the tv series, most of them used almost no orchestral sounds, so all of the samples were coming out of EXS-24 - my own custom samples, and some that were extracted / converted from Kontakt libraries, like a simple tremolo strings ensemble or something simple like that. I used their electric piano and organ instruments on every cue for the NBC series "Las Vegas" and they were great- better than any third party competitors that were available back then (early 2000's).
• I'd use a couple of Kontakt or a single Omnisphere instance on maybe 5 out of 50 cues on a feature, but almost never on tv. These would be when I really needed the true-legato-transitions of something like Tina Guo Cello, or the tempo-synced measured tremolos from Berlin Series, etc. So, only in emergencies.
• I do a LOT of extracting + converting Kontakt libraries to EXS-24 / Logic Sampler format, and although this eliminates any true-legato transition stuff, and I only get one mic position (usually I use the "mix" sample set), it gives me what I need for my hybrid scores most of the time.
• For analog synth emulations, I still use Logic's ES-2 90% of the time. I know it's 20+ years old and the UI is straight out of the 1990's, but I can get it to do beautiful cine-pulses that have tons of clean bottom end, better than most in terms of clean girth. I did a shootout which I posted on GearSpace a few years back, comparing all of the software MiniMoog Model D plugins against my hardware re-issue Model D, and for a laugh I put ES-2 in there as well. It stood up proudly against all comers. The only time I go third-party is when I need specialty features like the hard wavetables in Arturia's ProphetVS-V or the weird filter types in their Matrix-12v, or for specialized granular stuff like Pigments, Granite, etc., or sometimes Omnisphere. I posted comparisons between my hardware Prophet-VS and Xpander and the Arturia plugins, and I could get as close as makes no difference for the type of sounds I use. Nobody dared to hazard a guess, except for one guy who admitted that he took a piece of silence between the notes and boosted it a zillion db and discovered analog floor noise in the hardware clips that wasn't there in the software clips. Other than that tell-tale aspect, the sonic differences between the two were extremely minor.
• As to processing plugins, Logic's stock plugins have always been on par with the best of the third-party stuff for the most part. Their "vintage console" eq can stand alongside the UAD Neve (and my actual hardware AMS Neve 1084's) for most uses, and I even did a comparison with audio files that I posted on GearSpace a couple of years ago, asking people to guess which was which - UAD Neve vs Logic Neve vs hardware Neve. Again, almost nobody dared to guess. The only tell-tale was in the comparison between UAD Distressor and my hardware Distressors - the hardware reacted ever so slightly differently on the "pip" of each attack, while the software was identical each time around. Good luck picking that out in a full mix.
• But in recent years, some specialty and targeted plugins have eclipsed what Logic's stock stuff can do, like Waves Scheps Omni Channel, Waves "artist strips" like their dedicated JJP and Eddie Kramer Gtrs/Vox/Keys/Drums plugins (these are pretty great actually), and various other specialty plugins like ReFuse LowEnder, Ozone, BlackHole, McDSP SA-3, SSL and Brainworx console plugins, etc. Still, Logic's Tape Delay and Space Designer are on every mix I do, and their plain-jane compressor is still my default go-to until I need explosive destruction like from Kush UBK-1 or Pusher. In a GearSpace thread you'll find that Serben Ghenea still uses the ancient Metric Halo Channel Strip plugin as his default go-to for his chart-topping pop mixes. So old / cheap doesn't mean bad by any means.
• As good as Logic's stock plugins are, I still buy way too many plugins out of curiosity and "just in case". Almost 2,000 on my rig at the moment, all working perfectly. But my template is all stock plugins, and I deploy third-party stuff on an as-needed basis. The main reason I only used stock plugins for the tv series I did was because those ran for many years, and I was constantly re-purposing cues from season 1 into episodes in season 6, so I never wanted to be left out in the cold, and I never was. Similarly with the SAW horror movie franchise, which I've been scoring for 20 years now (!!!) and I still need to use excerpts from the first movie. So it's a good thing that most everything is stock plugins (or is bounced to audio), but that's a special case and not typical for most composers.
If I had to go back to stock plugins I wouldn't lose any sleep.