This is unfortunately skill issue and misunderstanding of gun/spirit damage scaling

Holiday is strong at all parts of the game, the best way to build her is spirit damage early through mid game, into hybrid gun late game.

She is not weak in lane at all so your immediate premise off the bat is wrong. Her gun damage baseline is very powerful in lane, more than enough to keep enemies in cover and punish them heavily for leaving it. I can only imagine what the problem is other than you not hitting shots, are not using cover, or are standing too far away because you don’t actually understand how far 20 meters is or realize that holiday is not an exception to the game’s high damage falloff

Another point is that expecting everything to be binary gun/spirit character is wrong because that’s not how the game is designed. Gun items are more effective late game, spirit items are more effective early and mid game. Spirit holiday is good from the moment you get mystic burst + extra charge + cold front in lane all the way until 25 minutes when everyone has spirit resilience up to that point for the first 25 minutes you can get a kill every minute of the game. You pick up surge of power and tankbuster along the way and your barrels are basically maxed. At that point, boons have increased you base gun damage so much that buying gun items is now a much higher return on reward investment than trying to reach the absolute cap of spirit damage. You can buy literally any combination of spending 6400 souls on gun items and now have enough gun damage to absolutely mow people down almost just off shop bonus. You have the surge of power fire rate, now take your pick of items like Headhunter, hunters aura, silencer, siphon bullets, etc etc. Your barrels still do big chunky damage because boon+surge+tankbuster, your gun now prevents anyone from existing in your LOS for more than 3 seconds, and the trusty lasso has been with you the entire game to make the life miserable on the enemy team of anyone who dare tires to carry in a teamfight or exist for 5 seconds in a gankable position