For the 'old age' part of OASDI, I basically concluded that it's a fantastic investment from 40 credits up until the first bend point, a mediocre investment until the second bend point (when including employer contribution, which I consider to be reasonable, arguments here notwithstanding), and a terrible investment after the second bend point. However, you should consider that with the OA benefit comes the Survivor and Disability insurance, which are wonderful (ok, I know the survivor benefit is very generous, don't know much about the disability insurance but assume it to be decent as well).
Overall, sure, I'd rather have had the control of this money from the get-go. I used to get up in arms about that. Now, as someone firmly wedged in the 0.32 regime (and who likely won't hit 0.15 due to FIRE), it's more of a shrug of the shoulders. Not in my circle of control, as MMM would say. I'll take the money - optimized however I can - whatever it may be once that time comes. Yes, I will get peeved if/when Congress reduces my benefit to fund the benefits of others, but I've self-insured enough so that it won't break me.