The development of this game is a long, slow, laborious process. Fact of the matter is, you will keep hearing this for years to come.
There are seven regions in Teyvat. Currently, the game has been out for about five months and only two of the regions have been created (Mondo and Liyue). The next region, Inazuma, is supposedly going to launch sometime in August according to some data mining spies.
It took three years to develop the game and launch last September with the two starting regions. The next region is taking about a year to make, along with other miscellaneous things like the monthly events, new characters and weapons, and a new small region in the Dragonspine mountains.
So basically you can expect each new major region to be released in around a year’s time. After Inazuma launches later this year you can expect another four years of development for all seven major regions to be released.
Somewhere along the way we will probably see the floating city region done as well, which is probably where the Goddess who beat you and your brother up is residing.
GenshinImpact is a game that will be around for a long time so no need to rush, not like you can rush anyway all your progress is inhibited by primogems (and the lack of it) as well as the scarcity of resin.