There isn't really a "second one". Overwatch 2 was just a patch with essentially two major changes. They changed the monetisation, making the game free-to-play and introducing the battle pass. An especially unpopular part of that is that new heroes now have to be bought with real money or unlocked through the battle pass. The other big change is the move from 6v6 to 5v5, which was controversial. There are definitely some positives, like getting rid of the "double shield meta", which did make the game more fun. But there's also more pressure and focus on the single tank.

The game is free and if you bought OW1 you still have all your stuff (cosmetics and all the non-OW2 heroes), so if you're curious you can just check it out. Personally I'm still enjoying the game but there's also a lot of valid criticism.