Open up device manager, find your wifi card, open its properties, and click the "Driver" tab and check who the provider of the driver is. One annoying thing I've found about Win 10 is that it prefers to overwrite perfectly functioning Win 8 or Win 7 drives with "Win 10 certified" generic Microsoft drivers. It also won't bother looking for manufacturer-provided drivers if a generic Microsoft driver is in place. A lot of times, these generic drivers simply don't work very well.
If the properties page reports that the driver provider is Microsoft, then you've probably got a generic driver in place. Go to the WiFi card manufacturer's web page, download their Win 10 driver, and install it. If they don't have Win 10 drivers yet, you can try the Win 8 or Win 7 drivers. Those usually work. But Win 10 will try to replace them with the generic Microsoft driver again during its automatic updates. There used to be an option to prevent updates from replacing a driver you've flagged, but Microsoft either moved or removed it in the October Win 10 update and I haven't been able to find it again.