Rega Planar 3 : Heavily upgraded yet produces a sound that I don't like


I have the Rega Planar 3 turntable for 30 years now. It had an original everything including a 100$ nottingham analogue cartridge/stylus.
Sound was not bad but pretty basic....
A few years ago I started upgrading it. I did all the upgrades together and the result is... not good. The sound is very accurate but it is too bright, there is almost no Bass and drums have no attack whatsoever.
I can't eliminate where the problem is because all upgrades are irreversible.
I know that the Ortofon Rondo Red has a very bright sound but still...

 

Here is a list of the upgrades :

1. ISOkinetik ISOvert Rega Tonearm VTA Adjustment Kit

https://www.analogueseduction.net/isokinetik-upgrades-and-parts/isokinetik-isovert-rega-tonearm-vta-adjustment-kit.html

 

2. Cardas Litz purple phono cable

 

3. ISOkinetik Tonearm Low CG weight

https://www.analogueseduction.net/isokinetik-upgrades-and-parts/isokinetik-isoweight.html

 

4. Ortofon Rondo Red Cartridge/stylus

 

5 Linn Linto phono pre amp (an old but outstanding piece which has a cult following).


6. I use Rega Elicit Apmplifer


triskadecaphobic
I had a Rega Planar 3 back in the mid 90’s.  It had a Linn K9 cartridge.  Sound was very lightweight and listener fatigue stopped me from buying records.   I ended up keeping the Rega RB300 arm from the Planar3 and bought a VPI Hw19.  I mounted the RB300 and Linn cartridge and there was bass again!  Sold the Rega TT less arm and was happy for a time. 
I would unload the TT here and get something else with the money.  
I am happy with the Elys II cartridge on my Planar 3.
I realize at $295 it might not be what you want to spend.
However I do think the Rega cartridges setup easily and are meant specifically for their TT so for me they just work. You’ll get various opinions for sure.

Regarding VTA, mentioned above, here are 2 images:
Humor me and remove VTA shim and felt mat. 
It may be worthwhile to identify the weakest link. With the weakest component intact, it does not matter how much you spend on elsewhere.

It could be the turntable itself.
Maybe the speaker or speaker cable.
Or the Rega amplifier or the interconnect.
I've been frustrated many times with similar reasons. Nothing can be more disappointing when you hear no improvement after spending $$$. However, it is a part of the business. Getting the right kind of combination and synergy among different components takes a lot of time, money, and efforts.