Regarding what #1 said about native glass being pricey, I agree. To keep your budget under $1500 and still get enough light for basketball, try these EF mount alternatives:

• Sigma 70-200mm f/2.8 DG OS HSM Sports for Canon EF
• Canon EF 135mm f/2L USM The Sigma is a total workhorse. If you dont mind a fixed focal length, that 135mm is exceptionally sharp for the price tho.

Unfortunately, native RF glass is overpriced. I had issues with f/4 lenses cuz theyre too dark in gyms.

• Canon EF 70-200mm f/2.8L IS II USM (Used)
• Canon Mount Adapter EF-EOS R

Regarding what #1 said about native glass being overpriced, I totally get the frustration, but you actually have some killer options if you look at the f/4 lineup. Honestly, since you are rocking an R3, you have a huge advantage! That sensor is a total beast in low light. Most people are scared of f/4 lenses in gyms, but the R3 handles high ISO so well that you can just crank the settings and get amazing, sharp shots without any issues. If you want to stay within that $1500 budget and get something brand new that just works, I really suggest looking at these:

• Canon RF 70-200mm f/4L IS USM
• Canon RF 85mm f/2 Macro IS STM
• Canon EF 70-200mm f/2.8L IS III USM The RF 70-200mm f/4 is fantastic because it is about the size of a soda can and fits in any bag. It is way easier to handle than those giant white lenses you see on the sidelines. Since you are in the bleachers, that zoom range is basically mandatory to see the action on the other side of the court. To stop the blur, just make sure your shutter speed is at least 1/800 or faster. Don't worry if the ISO hits 6400 or 12800, the R3 is designed for exactly that! You have an absolute dream machine in your hands, so just get out there and start clicking. You are gonna love the results once you get the hang of it!