Make sure you have a nose down grip. If you are nose up, and have a more overstable disc, it will stall out very early into flight:
https://www.discgolfreview.com/resources/articles/gripittoripit.shtml
The link to the grip mechanics is amazing! I turned 57 this year, and have been playing disc golf a bit more seriously the past 3-4 years. This summer I finally started getting some consistently better distance from focusing on the "brace" portion of my footwork. But I can see that I'll get a better rip if I first concentrate on my grip. I've heard about "nose down" but never really understood it. Now that I've visited (and bookmarked) the above link, it makes much better sense. I can't wait to get out in the field this weekend to practice!!
I've experienced the same problem with better plastic. I can't throw champion plastic worth a crap, so I don't even try anymore. Last year I bought a G Star Sidewinder and it took me a while to learn how to like it. Now it's my favorite forehand driver. I stick primarily to understable fairway drivers, and this summer I stepped up to 10 speed drivers. I developed a little elbow tendinitis this summer from throwing backhand too hard, so I added forehand to my game in a big way. Discs like Pro Wraith, Pro Beast, G-Star Sidewinder, and DX Valkyrie (all in the mid-160 gram range) get me a good reliable flight pretty consistently. My absolute favorite disc, though, is my X Stratus by Discraft. I can throw it anyway I want, and it always goes where it should. Laser straight, turn, or hyzer at lower speed.
It takes a while to find what works for you. Just keep experimenting.