Oh please. Everyone always blames the platform. Upwork per-project feels inefficient because your SOPs are garbage, not because the model is broken.
If your work is truly recurring, then your onboarding and documentation are the bottleneck - hire a solid VA to templatise that stuff, then scale on Upwork with fixed-price milestones. LinkedIn for ops roles? That's a joke unless you enjoy paying for someone's "culture fit" over actual output.
Retainers work when you've got consistent flow, sure. But if workload fluctuates, a retainer just makes you feel safe while you bleed cash on idle hours.
Real question is: are you trying to build a team or just fill a seat? if it's the latter, Upwork is still the least shit option.