In practice, with limited computational resource you only can generate few first character of Bitcoin address (e.g. 1YourBrand...). The rest of characters still looks random and near impossible to remember without any mistake.
It is impossible to create a Vanity address with too many customized characters like more than 8. It is discussed in
Vanity address (Mastering Bitcoin book)6. The frequency of a vanity pattern (1KidsCharity) and average search time on a desktop PC
Length Pattern Frequency Average search time
9 1KidsChari 1 in 7 quadrillion 800 years
That's true when we're talking about legacy address, i used 9 customized characters only as example. Although 9 customized character on legacy address is still possible with few high end GPU in few months.