You're not doing anything wrong. You have run into a common problem. The bridge cameras, like the SX series, have large zoom ranges - much larger than you can ever get with a DSLR.
A DSLR is much better for capturing actionn - faster focus, frame rate and less shutter lag. If you are enlarging a DSLR is better.
But, for pure zoom power a DSLR is not the best choice.
Did you ever get away from your SX510 for Macro? I just got a t6i this year, and blows away my old t5i. I'm finding that even cropping a pic way down still gives me a clear useable photo. I was originally surfing for teleconverter help with t6i. Have you used yours much? My 18-55mm kit lens provided some nice Macro, but I do not use it much anymore. I bought the 24mm and 40mm prime Canon lenses, cheap, and the photos are noticeably better. They are all f2.8 lenses. I also have the 55mm-250mm, which can do a good job of long Macro. BUT am looking at the 200mmL lens from Canon to replace my 55-250mm lens for more clarity. Interested to hear how you faired with your t6i. I tried out some 6d and 80d, and have not seen where those were better than the t6i, at all.
I tried out some 6d and 80d, and have not seen where those were better than the t6i, at all.
This thread is quite old. You might get a reply, but more likely not.
The 6D and 80D are much better camera bodies than the T6i. Their body shells are reinforced with magnesium, whereas the entire Rebel series is not. The 6D and 80D have a host of features the T6i lacks, beginning with AFMA, auto focus micro adjustment, which lets you tune a particular len to your camera body. They have much better low light performance. And, of course, there is more to it than what I have cited. It is an apples to oranges comparison.
As far as a 200mm lens goes, the EF 70-200mm f/4 USM lens is good enough to show you the difference between a T6i and either the 6D or 80D. You might look into that lens. There are four versions of it.
@The above shot was made with a 6D and the EF 70-200mm f/2.8L IS II USM lens @ 200mm, 1/125, f/2.8, ISO 10000. There was average room lighting, not spotlights. No flash, either.