USB 2? You might as well connect this via a wet string.
SATA III is up to 6 Gbps, And USB 3.0/3.1 Gen 1 at 5Gbps is a better match. And is supported on every USB port on you Mac. There is no need to be using ancient slow USB 2.
As for what you are doing, how about providing *exact* make/model/part numbers for everything here. SSDs, enclosures, adapters. Have you read the documentation about multiple drive support?
If you suspect problems with the hub why not try just connecting stuff directly to the MacBook Pro. But why do you expect this to work at all? And it's very confusing how you describe it, an external USB dock for two SATA drives should have the USB adapter part built-in and it has to provides the SATA port multiplier smarts to support more than one SATA drive on a SATA III link.
But why are you faffing around with his stuff? If you still can just return all this. You can pick up prepackaged USB and SSD drives at good prices, like the Samsung T7, and because that one is NVMe over up to USB 3.1 Gen 2 it's faster than SATA, and likely or has better passive cooling than whatever you are doing unless there are fans in the housing you used.
https://www.amazon.com/SAMSUNG-Porta...0874XWW23?th=1 or
https://www.amazon.com/dp/B08RX3343D...ter_B0B6MCKBT3
Or if you want better performance look at Thunderbolt 3 drives/enclosures.