"Just double click the keepass.kdbx" is not what it is. You need to go to your explorer, find the file in the folder structure and double click it. You then need to search for the website you are on and copy the password, then you need to go back to the website within 12 seconds and paste the password. That's inconvenient for everyone, but for a tech-illiterate grandma it's impossible.

Compare that to Bitwarden: You go to the website, click on the bitwarden icon and then click on the login details. Or even better, you can enable auto-complete with a single click and it automatically fills the login details when on the website, without clicking anything. That's far more convenient and easier.

Just as a FYI: My grandma has a sticky note on her laptop that shows exactly which buttons to press to get to her emails, with things like "Click this twice within 2 second, be fast!!" for a double click. It doesn't say "lef mouse button", she draw her touchpad and an arrow. She is not able to find her mails when the website changes the layout.