How did players like OTB-Redbaron and LLinusllove get so good? I'm trying hard to study using PIO solver. Still, it seems very overwhelming and difficult to implement those strategies in practice because of all the mixed strategies and assumptions that go into the solver solution. How should I approach my learning process more effectively?

I like a systematic approach by going spot for spot. So start off running a script (or with PIO basic bunch of sims) and try to study some SIMPLIFIED flop and turn strategies. Try to challenge yourself to figure out "why" solver is doing x. Run the sims with not too much sizings. When studying this for a couple weeks ingame it'
s important to put some extra focus on the specific spot you are studying. Do this for all the common spots in the game but keep always simplifying to not get overwelmed (and also you could start off merging UTG/MP vs BB srp or SB vs MP/UTG 3bp etc. , between BB pfr and sb pfr is reasonable difference tho).

Next step is to repeat that and slightly desimplefy step by step by adding more sizings or differenciate board textures more and more. At some point when you have a decent understanding of the fundamentals you could start tagging hands where you lost ingame and also put more focus on the river. I'm at this point right now so can't give you any advice afterwards

Also what really helped me a lot is to play simplified hand selection strategies. It's something you have to figure out for yourself when studying (you will get there) but avoid waisting time being too focussed on a certain hand. Also I see people here (including me, I did the same mistake) who play NL10<= and go super deep on the river while they have no clear idea what they are doing on earlier streets and I think that's a waiste of time imo.

For turns/rivers studying the "runout ev comparison hotmap" is really usefull imo. It's good to see for correlation between the 3 factors mentioned there: strategy, equity, ev.

GL man keep us updated in your approach

Thanks for a great reply! I agree with you that one should try to mastering flop and turn play before moving on to the river. And at the same time trying to implement simple strategies at first. I'm also really into theory which I found helped me a great deal in understand how to play many spots without studying that particular spot in pio beforehand.