If you pay, you'll be able to farm for these items longer in a day. But it will still take the same amount of runs.
The longest grind are artifacts. To get the best artifacts for one character you will need to clear a level 2000-3000 times. That will take you 80-300 hours pretty much no matter what. Now those could be over 100 days or it could be in twenty days, but you'll have to run the level as many times.
Also as other said, different f2p games work differently. In Genshin, you can easily complete the main request with free characters. Most people (like me), just pay to pull for particular characters they love. (Just check Hu Tao's character demo from their official yt account and you may get a glimpse how the characters (regardless of strength) are attracting themselves.))