this is ONE possibility (and my personal guess is the likely reason), but there MAY be different reasons.
But to try it without a Firefox started at the same time is fast, costs no money and is at least worth a try, possibly it helps a little.
If someone wants to do more than just occasionally “draw or paint a little”, then one should have powerful hardware because otherwise it gets frustrating very quickly. For occasional use, a current mid-range PC from 8 GB RAM upwards should be sufficient.
However, the opinions of users in the forum who use Krita intensively or even professionally, regarding the size of RAM “you should have” is at least 16 GB, but preferably more and a reasonably current CPU with at least 4 cores.
To save money, I have therefore bought a used graphics workstation (info on this can be found if you click on my profile picture). It’s 10 years old now, but it’s still very good because of its professional background and a new MacBook Pro would have been much more expensive.
Regarding the differences of Medibang Paint Pro and Krita. How do you explain something like that? Well, let’s try to make it tangible.
Please take a look at the size of the Medibang Paint Pro and Krita installations on your MacBook for comparison. Although I don’t own a PC from Apple I think you can compare the size of directories there as well. There you can visually “experience” that more capabilities, or a larger feature set, is reflected in the amount of disk space it requires. For example, Krita on my Windows PC is a good 3½ times larger than Medibang Paint Pro - for this I attach a screenshot of my PC. Well, and this more data occupies more RAM (memory) on your MacBook, plus image data and other things have to be calculated and so it can happen that Medibang feels “smoother” than Krita. A difference that should quickly no longer be felt with more powerful hardware.
Krita vs. Medibang Paint Pro, size on hard disc
That was a lot of theoretical talk, and hopefully it didn’t bore you too much. Maybe you have a friend with a newer PC where you can try out if Krita reacts acceptably for your needs to make a possible purchase decision?
If you have any questions about Krita, this is the right place for you. I cannot and will not give a specific PC purchase recommendation. Should you also want to buy a graphics tablet, if you don’t have one yet, make sure that the manufacturer offers drivers for your operating system, especially for Linux this is not a matter of course.
Good luck and happy painting!
Since it’s already 4:30 in the morning and I’m a lazy person, I translated this with the support of DeepL