Not that it's gospel, but at the time of the trade, Kirk was ranked the 27th most valuable player in MLB by Fangraphs. As of July 21, 2023, he was still ranked 39th. Moreno wasn't Top 50 in the most current rankings. Obviously teams will have their own valuation systems, but you are correct that at the time of the trade, Kirk was rated higher than Moreno. In fact, coming off a 3.9 WAR, 129 wRC+ season - I think everyone should have considered Kirk to be the better player (currently). The real question was whether he would stay 'above' Moreno over the long term. This year, they were similar in value and obviously, based on the playoffs, everyone expects Moreno will just bud into a superstar next year. That may happen - but then again, we all though Kirk was on the same path heading into the 2023 season - so you never know.
To be honest, I wouldn't be surprised if Kirk posts a 4 WAR year, while Moreno struggles to a 2 WAR season. I also wouldn't be surprised if Kirk was at 2 WAR and Moreno was at 4 WAR. Young catchers are often quite unpredictable. Even Adley declined (a bit) this year after an incredible rookie season.