Zavato, I set VTF on my Axis with a ruler and it is horizontal to platter; I was told this is correct position.
VTF = Vertical Tracking Force (aka, downforce): the vertical force applied by the stylus to the record suface. It is measured with a balance or a scale, the same way you measure your body weight. One doesn't measure stylus downforce with a ruler, nor body weight with a yardstick.
Adjusting VTF by making the tonearm or cartridge horizontal to the platter could result in downforce that's much higher or lower than the internal suspension of the cartridge was designed for. Whoever gave you this advice was wrong (or you misunderstood it).
One makes the tonearm or cartridge horizontal to the platter by adjusting the mounting height of the tonearm at its base. One adjusts downforce (VTF) by moving the counterweights on the arm stub and/or adjusting the VTF dial (if the arm has one). These adjustments are separate, although their effects are interactive.
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FWIW... I have no personal experience with Rega cartridges but I've seen umpteen posts like Diggory's over the years. I've never seen anyone rave about how much better an Elys sounds than whatever it replaced, but I've seen many posts raving about improvements when an Elys was replaced with something else.
Ebm's post also makes sense to me. The fact that rock recordings sound okay means little. Rock music is *supposed* to sound distorted. Guitar amplifiers have adjustable distortion built in and more is often added during mixing and mastering. No one but the sound engineers actually know what any particular rock record should sound like.
OTOH, classical and other acoustic music provide some sort of absolute standard (depending on one's hearing of course). Anyone who attends live performances has some idea of what violins actually sound like. Distortions introduced during playback are a departure from one's internalized ideal and are more readily audible as "wrong" than the same distortions in music which is *meant* to sound distorted.
Try a different cartridge and have it set up properly (or, better yet, learn to do it yourself). The suggestions on Raul's lengthy MM vs. MC thread may be helpful.