Yes, the get streams endpoint only gives you the viewer count for each individual streams, but that’s why you’d page through and sum the results.
You can even filter the results so specific games, so you can make parallel requests, one for each game, and page through each individually. Some games may only have 1 or 2 pages of results, others may have hundreds, all depends on what games you want data for.
If you are the developer/publisher of those games and have claimed ownership for your organisation on Twitch then you’ll have access to those games analytics. If you’re not the developer/publisher, and have not been granted the scope to access that data by the developer/publisher, then your ability to scrape data will be very limited and have significant degree of inaccuracy.