He's a solid defenseman and makes us better. Doesn't mean we can afford him, and someone needs to go to Seattle.
Getting out from under his contract next year certainly makes us worse on D next year, but relative to our other choices in getting salary down may only be marginally worse than other options. Being free of his that cap hit in his age 34/35/36 almost certainly makes us better in those years, along with the future assets we save by letting Seattle take him to incentivize them to also take TJ or similar.
We should absolutely celebrate him while we have him, and if he's one of your favorite players I get how hard it is to think about losing him.