Whom should I blame when Wi-Fi works on my phone but Windows says "No Internet, secured"?

"No Internet, secured" means the laptop joined the Wi-Fi fine but cannot reach the internet, and since your phone works on the same network, the router and ISP are probably fine. That points at something on the laptop. A quick way to split it up:

• Open Terminal and run ipconfig. Look at the Wi-Fi adapter. If the IPv4 address starts with 169.254, the laptop never got an address from the router. If it has a normal address like 192.168.x.x, note the Default Gateway.
• Run ping followed by the gateway address. If that works, then ping 8.8.8.8. If 8.8.8.8 works but ping google.com does not, the problem is DNS, so try setting DNS to 1.1.1.1 or 8.8.8.8 on the Wi-Fi adapter.
• If nothing works, reset the network stack as administrator: netsh winsock reset, then netsh int ip reset, then ipconfig /release and ipconfig /renew, and restart.
• Turn off any VPN or proxy (Settings > Network & internet > Proxy), and check that Wi-Fi power saving is not on for the adapter in Device Manager (adapter properties > Power Management).
• Update or roll back the Wi-Fi driver from the laptop maker's site, since this exact symptom is often a driver issue after an update.

If the laptop also fails on a different network, such as a phone hotspot, it is the laptop. If it works there, the router settings (such as MAC filtering or a DHCP limit) are worth a look.