It’s a trust issue. There’s no one more of a PITA than a new team member who joins and starts questioning every little thing and demanding it be changed (the initial questioning is fine, so long as you accept “because” as a reason). OF COURSE any team that’s shipping software will have things that don’t make sense prima facie, because they’re accumulated tech debt or historical accident.
Go beyond identifying all these problems towards solving them. Choose a small problem, where you won’t have to fight and argue, just a little dust bunny you can sweep out of the way. Do it again, and again, and again. This is how you build trust. As you build trust, it becomes easier to seek change.
Additionally, you may also find that not all the little problems are worth solving, and what’s more interesting are the bigger problems around product-market fit, usability, and revenue.