I confess to sharing Ancient One's ambivalence to the Speedforce concept, while often a writers godsend it is indeed a very lazy catch-all plot device when all is said and done, one that is used to generate story potential but also to wave aside consequences and impose entirely arbitrary limitations/possibilities on The Flash.
Still, it sits in the same place as The Source or the Quantum Field do in the DC Universe and could be said to be an expression of The Source itself. I don't think this has ever been said to be the case, but if you look to Rebirth #1 and last seasons television interlude as Barry struggles to regain his speed while lost within the Force it does seem highly likely that the Force and The Source are indeed two sides of the same coin, spanning dimensions and realities and existing outside of them. What Barry and others see while within it is likely to be as much their own projections being played out as it is any sort of reality or actual independent sentience...
Now that you mention it, that was pretty much the big reveal of the the pretty much forgotten Genesis-mini back in the day, ´stating that most of DC's metabeings were linked directly or indirectly to the source, were in fact demi-gods and that the Quantum field and Speed-force were lesser extension of the Source or also linked to it.
It gave pretty much a unifying explanation for DC's superbeings just as the Celestials genetic tampering are the explanation for Marvel's superbeings.