Well, a small rack in my view is a recipe for frustration when one doesnāt yet know the modules one likes best, because hp is at such a premium.
I would say a complex oscillator is a window into what modular is all about and a source with tons of possibilities and fun.
I had no problems coming to grips with FG when I purchased it starting out with eurorack. On a simple level it can be treated as two separate oscillators with sync and multiple taps. The layout is intuitive.
FG in particular has built in tuners, and can do FM, AM, ring mod, linear and expo switch, LFO switch, noise mod etc. Personally I think it requires less skill than patching FM and AM with external VCAs, not to mention even/odd high/low waveshaping.
For example, look how much more expert this is
https://www.muffwiggler.com/forum/viewtopic.php?t=76009&highlight=intellijel+west+coast
Also using a random osc to FM another one doesnāt always sound that good, whereas the oscs in complex oscillator are already matched for this.