Those publications' content are ephemeral and age quite fast, you don't learn much that can help you develop over time.
Those subscriptions aren't very helpful on what you want to improve, they are good for you to understand the current economic scenario and new hypes and booms, and each have their own biases. I'd prefer HBR over the others.
They are also good for you to keep up on subjects so you can talk with other people that are business types.
And for one, Farnam Street essentially suggests doing the same thing.
A very similar approach to what parent suggests is in the book "How to Read a Book". It starts with explaining regular kinds of reading, and ends with synoptical reading - where you have to actually go and make a lot of effort to analyze, compare and contrast the current book with other stuff you have read.
Anyway, nothing grows soft and hard skills more than actually doing the legwork - just passivereading will not do much; active reading might help, but mixing reading with going out and actually doing stuff will help the most.
There was some good stuff; it had the best explanation of the Business Model Canvas and how business models worked, but that's the one memorable thing I got from HBR. I'd say pick one of the others - I'd second the recommendation for Financial Times.
I was always reluctant to ask people for mentorship or help, but when someone reached out to me for questions, I helped them immediately. I don't think I'm that much of an outlier in terms of helpfulness, so I'm sure other people are just as happy to help.
I would try and reach out to people whose business you admire but that aren't competitors. Make sure you close the loop and tell them how what you tried based on their advice, how you benefitted etc.