What size boot do you wear - we might be able to get you a "test drive". I have a pair of
Excellorators I could loan you, if they would fit, if you are willing to pay for shipping both ways.
In case you did not notice my avatar - I also dive "vintage" gear that cost way less than my fins and that perform better than the current plastic gear. I don't own ANY modern plastic gear (all mine is metal). But that does not mean that there are some things that can't be improved with modern technology. Fin design and fin material can and do provide improved performance (at a price). But the cost of fins amortized over a lifetime of diving is pretty insignificant. In order to keep old regs going, they require periodic overhaul which should be factored into the lifetime costs - a pair of fins can be a once in a lifetime expense (OK you might have to buy new straps every 10 years
).
I don't know if Tan Delta Excellerators would work that much better for you - I know they did for me, solving several problems - but to dismiss them just because of initial price could be very short sighted.