New MTB makes it feel like too much weight on arms? How do I make it better?
What I can tell you is limited without knowing further details like the model of both the new and old bike. But, looking at the geometry chart, seems like the new bike is most likely an XC/backcountry bike. The geometry on XC bikes is optimized for going fast on flat and uphill, so the stems are longer. However this bike seems to be halfway between a trail bike and an XC bike, as it has 120mm of travel and has a slacker headtube angle than most XC bikes.
So, without being able to look at your old bike to figure out what it was that made you more comfortable, my best guess is that you are used to a shorter stem. Try switching to a smaller stem, but make sure you also get wider bars or the steering will become very awkward. The longer the stem, the skinnier the bars should be and vice versa. Also, as stated in the comments, the bike may just take some getting used to. When I made the switch from XC geometry bikes to trail bikes, for a few weeks it felt like everything was off. But now I'm used to it.
I hope this helps. It's the best I can do without seeing both bikes.