Technology

TL;DR: your statements are incorrect and you're being assumptive.

Steps 2 and 3 of your method already make it way too hard to remember

Step 2 is "hard"? Seriously??? It boils down to "first letter of each word, as it's written, plus punctuation".

Regarding step 3, I'll clarify further near the end.

Just pick like 6 random, unconnected, reasonably uncommon words and make that your entire password

That's a variation of the "correct horse battery staple" method. It works with some caveats:

1. Your method does not scale well at all. If you try to harden it further, by using more words, you hit Miller's Law. My method however scales considerably better because there's some underlying meaning (for you) on what you're using to extend the password further.
2. Even in English, a language that typically uses short words, your method requires ~30 characters per password. Larger and less dense passwords are actually an issue because some systems have a max password size, like Lemmy (60chars max). My method however uses less characters to output the same amount of entropy.
3. The least common the word, the more useful for a password, and yet the harder to remember. With synonyms and near-synonyms making it even harder. Typically less common words are also longer, making #2 even more problematic.

The average English speaker has about 20k words in their active vocab, so if you run the numbers there’s more entropy in that than in your 11 character suggestion.

I'll interpret your arbitrary/"random" restriction to English as being a poorly conveyed example. Regardless.

The suggestion is the procedure. The 11 characters password is not the suggestion, but an example, clearly tagged as such. You can easily apply this method to a longer string, and you'll accordingly get a larger password with more entropy, it's a no-brainer.

For further detail, here's the actual maths.

• Your method: 20k states/word (as you specified English). log₂(20k) = 14.3 bits of entropy. For six words, as you suggested, 86 bits. The "capitalise the first" and "add 1 to the end" rules do nothing, since systematic changes don't raise entropy.
• My method: at least 70 states/char (26 capital letters, 26 minuscule letters, 10 digits, ~8 punctuation marks); log₂(70)=6.1. Outputs the same entropy as yours after 14 chars or so.

Now, regarding step #3. It does increase a little the amount of entropy. But the main reason that it's there is another - plenty systems refuse passwords that don't contain numbers, and some even catch on your "add 1 to the end" trick.

EDIT: I did a major rewording of this comment, fixing the maths and reasoning. I'm also trying to be less verbose.