As the process progresses the quick results take longer. The first half of the battle is to kill the algae and then it shifts to removing / filtering out the dead stuffs. It can be cloudy or milky at this stage and the filter is going to be the deciding factor on how fast it clears. But. similar to the early green stages, as time goes on it gets harder to see the progress. Say you get the volume of the pool filtered. Due to mixing maybe only half of the pool water was filtered. On the second pass, half was filtered already and wasted the opportunity to get more. With each additional pass, you re-re-re filter, even more water that was already filtered. For most folks the last bit is miserable to wait out. It’s just enough to not be perfectly clear and drags on. Yours stalling much earlier than that points to the filter not being great for this task like Marty mentioned above. It will work, but it could be a while.
At the end of the season, people will be looking to unload a lot of equipment. Either they got rid of the the pool or got new stuff in the blowout sale and are selling their old stuff. Check FB Marketplace and OfferUp regularly and you can probably score a great upgrade on the cheap.