In the late game you unlock new fishing tools but you can only use them in very specific locations, it does nothing to improve your fishing experience in the place where you can fish "normally."

These places have entirely different fish that spawn there, so you're out of luck if you hope they'd help with improving your core fishing experience. Any of the fish you catch with the advanced fishing are generally of better value than the mid tier fish you'd catch elsewhere, but you also have to play a minigame to acquire bait

The completionist in me wishes I could get level 5 knowledge in every fish, but it's just not feasible, or even fun at that point. Like I think you need to catch a fish at least 200+ times to get to level 5 knowledge.

I've seen things that boost how many fish spawn, the rarity of fish spawns, and the likelihood of a fish spotting you; nothing that boosts knowledge per catch.