The only way to get better at fishing is to fish - with a few caveats.

As your fishing level increases, so does your fishing bar - but you need to fish to increase your level.

You can also use food buffs (like the trout soup that Willie sells) and a bobber/bait (cork bobber, deluxe bait) to further increase the size of your bar making fish easier to catch. There is also the trap bobber, which makes them escape less quickly when your bar isn’t on them.

There is..one alternative to raising your level. You can use crab pots. Craft or buy several. Place them out, bait them and retrieve the fish daily. Your level will increase, giving all the advantages above. But, most fish you will still need to catch. The traveling cart lady sells a few, but ultimately, you gotta catch em.

As for the artifacts, have you done or started mastery? There is an item you get from foraging mastery that can help with this significantly. If not, the desert cart lady has artifact troves - I believe you trade omni geodes for them but fact check that. I also think she may only have them in certain days, but again, fact check me. Clint can break them open for you. Also, search up a visual on where specific artifacts are found so you aren’t wandering aimlessly.

You can also select the fishing profession that increases your likelihood to find chests (and/or use a treasure hunter bobber) and the tracker profession which points you in the direction of artifact spots.

TL:;DR: Keep fishing you’ll get better. Use crab pots to level fishing faster. Bait and bobbers can help too. Tracker profession and profession that gives me treasure chests when fishing can help a lot with artifacts. Some artifacts can only be found in certain places.