Why isn't this DataStore script working correctly?

I'm trying to get my DataStore script to automatically detect all the stats in the player's stats folder, as there are many, and save/load them all accordingly. For some reason however, it's either not saving correctly or not loading correctly. When I run the game, set the values of the stats, then leave, when I rejoin all of them are back to their default values instead of the ones that should have been saved.

local dataStore = game:GetService("DataStoreService")
local players = game:GetService("Players")

local statsStore = dataStore:GetDataStore("StatsStore")

function playerAdded(player)
    local playerGui = player:WaitForChild("PlayerGui")
    local statsGui = playerGui:WaitForChild("StatsGui")
    local playerStats = statsGui:WaitForChild("PlayerStats") --the folder where all the player's stat values are stored

    local key = ("player_"..player.UserId)

    local savedStats = statsStore:GetAsync(key)

    local statsToSave = {}

    for _, playerStat in pairs(playerStats:GetChildren()) do
        statsToSave[playerStat.Name] = playerStat.Value
    end

    if savedStats then
        for statName, stat in pairs(savedStats) do
            local playerStat = playerStats:FindFirstChild(statName)
            if playerStat then
                playerStat.Value = stat
            end
        end
    else
        statsStore:SetAsync(key, statsToSave)
    end
end

function playerRemoved(player)
    local playerGui = player:WaitForChild("PlayerGui")
    local statsGui = playerGui:WaitForChild("StatsGui")
    local playerStats = statsGui:WaitForChild("PlayerStats")

    local key = ("player_"..player.UserId)

    local statsToSave = {}

    for _, playerStat in pairs(playerStats:GetChildren()) do
        statsToSave[playerStat.Name] = playerStat.Value
    end

    statsStore:SetAsync(key, statsToSave)
end

players.PlayerAdded:connect(playerAdded)
players.PlayerRemoving:connect(playerRemoved)