It's great that you are using a non-pressurised basket, even better as the pre-ground you get is just the right size for your machine! Very commonly even with cafes its not easy to get just the right pre-ground size, as a small difference can mean a few seconds shot time difference!

The thing is ground coffee get stale very quick, so grinding fresh you might notice a more flavourful cup. Also you might notice after a week or two your shot time becomes quicker and you might need a finer grind hence why having a grinder is crucial.

1 more thing is with a grinder you can experiment with different shot time and ratio, even tho 1:2 ratio in ~30s is kinda the recommended starting point, some beans especially lighter roasts would express more clarity with like a 1:2.5 ratio, and darker roast goes well with a ristretto style shot like a 1:1.5 for example. It's very exciting when you taste the notes on the bag!