My pro controller is drifting. First the left joycon, then it starts drifting after getting it fixed, then the right joycon, and now the pro controller. I've had a rotten luck with Nintendo controllers this gen, considering I can still use my knockoff GC controllers and Wiimotes without issue. Is there any easy way to fix the drifting on a pro controller? And if not, is there a 3rd party controller to replace it? Especially the joycons, I'd really like to have joycon-like controllers that actually work well. 

Send it in for repairs.

If you have a valid guarantee then just send it for repair, otherwise I did have a single episode of drift of few months back and all I did to "fix" it was simply to spin the joy stick like a madman a few times and it stopped drifting since thankfully.

Though mine has 6 years of activity now, so I kinda be expecting the hiccup there

Its guarantee is already expired, sadly.

Replace the stick itself. The parts are generic from China. But the real solution is to buy a 8bitdo Ultimate Controller. It uses hall effect sticks meaning no drift. It's worth the price. Costs the same as pro. Better built. You just lose NFC

Does it have motion controls?

Firstly I don't think the quality is as good as past Nintendo controllers for either the Joy cons or the Pro controllers.  I have been through half a dozen Pro controllers.  I play almost exclusively docked so while my launch Joy Cons have not developed drift they also have likely less than 20 hours of play time. We have been through 4 sets of Joy cons on the kids switches. Considering the price I am very disappointed in Nintendo on this.  Their stuff (controllers/ consoles) used to last decades up to the Wii.  Now I don't think you are unlucky I think Nintendo has finally gone too cheap on components.

As for your question I might end up trying one of these controllers as well since it looks like the only things sacrificed are NFC and battery life. Motion control is there.  It is a Pro style controller though.

From Amazon:

About this item

• Compatible with Switch and Steam Deck via Bluetooth/2.4g adapter/USB Cable, Windows with a 2.4g adapter/USB Cable.
• Multifunctional Charging Dock - Stable connection and controller will be automatically switching ON/OFF while it is undocked/docked.
• Hall Effect Sensing Joystick
• Ultimate Software on PC and mobile (Android/iOS)
• 2 Pro back paddle buttons, Custom Profile Switch Button, Player indicators & 2-way Mode Switching button.
• Rumble vibration, motion controls, USB-C, 22 hours rechargeable battery.

Push down on the stick for about 30 seconds, try to blow out any dust.

The quick and easy DIY fix for stick drift is to use an electronic cleaner spray. This is what I have: https://www.amazon.com/CRC-05103-Electronic-Cleaner-11/dp/B000BXOGNI

I don't have a Pro Controller but it works well on the joycons so I assume it'd work on the Pro Controller. It's not a permanent solution, you'll have to respray maybe every several dozens of hours of usage once drift starts up again. First time I used it I had to spray a second time shortly after that, but since then I only need to spray once after many hours of play. It's easy, cheap, and DIY and fixes it for a while so it's much better than any other solution I've heard of considering Nintendo never actually bothered to fix this issue in their Switch controllers.

Push the stick into any direction, get real close to it and blow out all the dust you can on the side opposite to where you pushed it. Then repeat this in several directions, I usually do 3 or 4. Then spin the stick around like a dozen times, and another dozen times the other way.

I know that sounds stupid but in my experience it does temporarily fix the drifting.