I think the problem with gigs is less their actual content, then how you are introduced to them.
First of all, Fixers are introduced poorly. I think the first Fixer I got a call from was Regina. I did not know who she was, why she was calling me and why she was all like "Hey V! My fav Merc! Do this and that for me, because reasons"...
This is especially jarring, because the game goes out of its way to say that Fixer relation is one of the most important things and you have this long talk with Dex as part of the Main Quest, just so you can get work from him... I think you should have had to meet every or most Fixers in person before they offer you Gigs. Youtuber "NeverKnowsBest" makes a few very good points about this:
(Warning almost 2 hours long)
The second major Problem is how you then get the gigs: You trigger a phonecall when you are near a Gig-marker on your map. You can't ignore the call and basically get an exposition dump by those fixers whether you want it or not (when you engage in Battle at least V cuts them short). It would be sooooo much more immersive, if for some of those quests you had to call the fixers and they gave you a mission at random.
Then, lastly, I think the game suffers from it's always on objective tracker, which leads you straight to the targets... Especially the "find something" or "steal something" missions would be so much more gratifying if you could just look for the bloody thing yourself and not just follow a marker (sometimes this is actually the case with a more generic "area of interest", but more often then not your led straight to your target).
Long story short: The gigs are actually great and not really inferior to the Witcher's side quests. They just need to be presented in a less robotic and more seamless fashion.