Bear in mind that each successive version of Lightroom will have been developed on the assumption that users will be running it on progressively higher-resource machines. (Forget the laughable "minimum system requirements" that Adobe quote for all their products - that is merely a sales ploy).
Not a sales ploy...it's simply the lowest hardware that Adobe tests against and officially supports. More is always better.
So, in my experience, here's the breakdown of LR bottlenecks...it's similar to Photoshop but importantly different.
Top of the ladder is processor speed...
The second is multi cores (although that tops out quickly, 2 cores is almost 2x better than single core but 4 cores is not nearly 4x, more like 2.5-3x at best).
The third is 32 vs 64 bit processing which 64 bit being at least 20-30 % better depending on ram. If you are under 4 gigs then the difference is more like 10-15%.
Ram...but past a certain point it doesn't matter. This is really where Photoshop and Lightroom are fundamentally different. As long as you have 8-16 gigs of ram on a 64-bit machine, that's the best you can expect for Lightroom. Adding more won't help. But regarding Photoshop on 64 bit machines, more ram is indeed important. I have 32 gigs and wish for 64 gigs on my main workstation...particularly when I'm working on pans from my IQ 180 files :~(
The last bottleneck is HD speed. Lightroom is constantly reading and writing lots and lots of little files to the HD. If you drive is optimized for large block writes (like you might do for Photoshop) it may actually slow down small block reads/writes for Lightroom. Faster HDs can and do make Lightroom seem much faster.
Aside from increasing the speed of your CPU or adding cores, the three things you can do to speed up LR is go 64 bit, add ram to at least 8 gigs (16 is better if you need to run LR and Photoshop) and get really fast HDs. It's ideal if you can keep your catalog and previews on a different physical drive than your images. And it's ideal if your catalog and previews are on a really fast non-boot drive (if the OS starts paging it really slows down disk access).
SSDs can make Lightroom fly, but are expensive...stripped arrays can boost speed (as long as you back up cause stripped arrays are fragile).
Lightroom is not really bloated...it's doing a ton of little things and a few big things. The fact the programing is done in Lua is part of the performance issue...the other part is that in reality, LR is a really heavy database app with tones of UI and interface performance requirements. But I'll tell you that will not change...
So there you have it, my best suggestions for looking at speeding LR up!