I feel your exact pain. I have a BT army as well. I shelved it for now and I now running with Ultramarines, who do quite well with Guilliman. I love the colors of my BT's and I poured a lot of time and money into them. But they don't do well in 8th. Then again in 7th I beat orcs and tyranids all the time. GW is doing their balancing act. IG sucked in 7th, Eldar and Tau ruled. Now it is reversed with IG on top. Marines are mediocre in CC in this edition, which means BT are now a mediocre army, and without librarians, they are further hampered. But a lot of armies are so so. Necron players are upset now, Chaos players were upset for years, and now they are doing better.

But the reality is the GW needs to make money, or we don't have this hobby any more, so there will be changes and changes and armies tiers will change.

So, I mean if you want to play a gunline, UM have the best gunline for marines ATM. If you want CC, then playing BT, Space Wolves, and other CC marines is going to be challenging.