My laptop only has 1 bar Wi-Fi whereas my cell phone has full Wi-Fi. I've often plugged the wireless router in and restarted my laptop more often, but I still only have 1 bar of Wi-Fi.
The WLAN can be connected to 2.4 GHz (n standard) or 5 GHz (ac standard). You should know this difference in order to make comparisons.
5 GHz WLAN has a shorter range, so the signal strength is lower at 5 GHz, but 5 GHz WLAN often has a data rate that is 3 times better. Check that out.
Is Bluetooth active on the laptop, because Bluetooth more or less interferes with the 2.4 GHz WLAN. 5 GHz WLAN is not disturbed by Bluetooth. Turn off Bluetooth.
If the laptop is very old (often opened and closed), the WLAN connection between the WLAN module and the WLAN antenna (which is built into the lid) can be interrupted or lost, which means that reception is also poor.