I believe we can learn languages by (1) concentrating on mimicking and (2) learning by speaking with others and being continuously corrected by others.
The problem is that is requires a tremendous amount of work for learner and teacher.
Think how a baby or child learns and do as much of that as possible.
Initially absolutely avoid all reading, and totally avoid learning any rules.
Improve your general ability of mimicking skills e.g. by copying singers and songs, by copying famous people in the foreign language, mimicking accents or people in your own mother tongue.
People with English as their mother tongue have some advantages - we actually recognise a huge variety of vowel sounds because various English accents contain them - we also have familiarity with a variety of grammatical constructs. We also know pronunciation and writing are completely disjoint: anyone coming from a language where you say what you read has a big disadvantage.
Much of my belief comes from talking with people that have English as their second language, and looking for their successes and failures. Some people learn English well and it's interesting to look for why them? Some mistakes are common to particular groups and it's interesting to look for the root cause.
I have applied some of the above to teach myself conversational Spanish. To test my beliefs I'm definitely keen to move onto something more difficult ( I'm middle aged): the block is that I will need to dedicate many months of effort living in another country.
