It depends on your definitions of easy to remember, hard to guess. 6 dictionary words with one random character is sufficiently complex to thwart planetary scale brute force attacks. It's much easier to remember than 20 random ascii characters.
I use the first three letters of each word in book titles/song lyrics and a number that means something to me like 186282 (speed of light in a vacuum in miles per second) for master passwords everything else is stored in Keepassxc.
aphiofsofdes68537513 is good enough and defeats a dictionary attack.
It requires discipline but I’m responsible for people’s PII at work and I treat that seriously.
For my personal stuff I keep a separate vault but with the same criteria.
I did something similar but you really should get some randomness in there. If an attacker is brute forcing solutions, it's conceivable, even likely, that attackers are going to smash together datasets like song lyrics or anything that comes up high in a google search to prioritize the search space. You could search millions of permutations of song lyrics for the 50% most popular songs on Spotify. You could do the same with text previews for books on Amazon. It probably wouldn't take that long for a targeted attacker.
If 2fa is involved it's a different story, but if you're talking about something liiiike the pass key of a private key that you can't guarantee is secret? Or if it's the private key used to do things like sign certificates? Please add randomness.
