Lightroom super slow

So since the big update last fall, my LR has been ridiculously slow.  It freezes up all the time, takes FOREVER to process my images just so I can even look at them clearly.  I was having issues before the big change, needless to say the big change didn't help anything.  I used to be able to scroll through 1000 images, cull and edit in an hour, now it takes several because I can barely see them to see if I want to keep them or not and scroll onto the next image.  I got a new computer, DID NOT CHANGE A THING! I'm a little pissed that I dropped $3000 on something that is not going to help my workflow.  My previous computer was 5 years old so I assumed, like an ass it was that.  My new computer is a MacBook Pro, OS 10.13.6  2.7 GHz processor, intel core i7, 16 GB memory and Intel Iris Plus Graphics 655 1536 MB.  Plus 1TB of storage. I called Adobe and they took over my computer and changed a bunch of settings that seemed to help for about an hour, then it started lagging.  I shoot a Nikon d750, so my files are large, like 25mb.  I would think by now Adobe would have come up with faster software to keep up with these large files.  I'm editing directly from my computer so its not like an external drive is slowing me down.  Am I the only one having these problems???