Thank you for the report. Normally I wouldn’t consider this a bug per se, but I’m not too sure where else to put this. Perhaps #feature-requests ?
Performance optimization is always an ongoing thing - in each version we get to experiment with it here and there. Often times though it ends up breaking things, or introducing some kind of artifacts like flickering or improperly rendered results. So we have to be careful in our approach.
There’s also a limit as to how much we can optimize. You’re on a mid-level low-power laptop CPU from 2015, which is going to struggle quite a bit more than a more recent desktop CPU. Also it’s pretty reasonable that the bigger the file, the slower it gets, there’s really not much we can do about that.
That said, you can be rest assured that we do take performance seriously and we are fairly experienced in optimizations. Things will get better gradually, but I hope you’ll understand that the more performance we squeeze, the harder it gets to optimize even more, so it would take more time as a user to see improvements.