My wireless adaptor (TP-LINK TL-WN822N v3.0) uses the rtl8192cu module by default, which is apparently old and terrible; the symptom I see is 72KB/s download speeds.
The modern fix for this is apparently the rtl8xxxu driver, which is built into the kernel since 4.4, but only when CONFIG_RTL8XXXU_UNTESTED is enabled. Apparently on most other distros that's now enabled, and hence that driver can be enabled just by blacklisting rtl8192cu (see e.g. these instructions for Ubuntu).
For more more information, please see the README for this repo, which is an interim fix that's now deprecated in favor of rtl8xxxu.