I don't know if you use sysbench software. I plugged a USB stick into a USB 3.0 port and got 64 Disk I/O marks. An ordinary hard disk gets 805. I wonder if it should be that slow?
No, it shouldn't be that slow, but USB sticks are mostly garbage, and most of the cheap ones won't be anywhere near as fast as USB 3 is designed for (I have a couple that don't run any faster than USB2 sticks in windows 10 too). You need the expensive sticks, with high data rates, and even then they probably won't run at USB 3 design speeds. I get the most consistent, and fastest speed, using a HDD enclosure with USB 3. I don't have a SSD to try in it, but that should be even faster. I haven't measured the speed with SysBench, so I can't give exact numbers.
I also find that different controllers impact the speed. The best one, that I have, is a SUPAHUB brand, which has a Renesas chipset (I got it at Amazon). In fact I now have two of them, and they seem to be very good. I also have one that is a cheap generic thing, branded as Fresco Logic. It does not have any way to add additional power, and it is easily overpowered (it powers off) because the PCIe socket cannot supply enough power for it (at least on the two systems where I have tried it). When it does work, it seems to perform okay.
One other thing, is that the A type connectors can fail to connect to USB 3, and it may be running with the USB 2 controller, at USB 2 speeds (USB 3 controllers have two controllers, one for USB 3, and another for USB 1.x and 2.x - both are operated by the USBXHCD.SYS driver). Those connectors need to be close to perfect, to avoid connection problems, and it is very difficult to determine what connection it is actually using. Interestingly, they can also fail to connect to the USB 2 controller, which only matters if you are using an external USB 3 hub, or a USB 2 device.
It is also likely that the USBXHCD.SYS driver is still loaded with debug code, so there is some hope that it will get better, eventually.