Best way to improve

Blitz may be fun but many people believe that slow chess, where you have a chance to think, and studying is a much better way to improve.
For example, you drew this position, although you had more than two minutes left on your clock:

Blitz is a good way to practice new openings relatively quickly as well as developing pattern recognition for newer players. Tactics puzzles are better than blitz for the latter. On the whole, though, blitz isn't a good way to improve - especially for beginning players. You'll pick up bad habits easily, like using intuition instead of analysis and calculations to choose your moves. Blitz is fun, but if you really want to improve work on tactics and player slower time controls.

Then I switched to blitz. My rating almost complete flatlined over more than 5 months. Even though I watched videos and read articles, my improvement was minuscule.
Then I switched back to rapid. My rating went to 1500 in a couple months.
Rapid is way, way better for improving. Blitz develops bad habits. It's good for experimenting, or working on a very new opening. But improvement in general lies in rapid (or longer) games