If you've not had a road bike for over 20 years, then I'd think that your core strength (and possibly suppleness) would not be optimal for a road bike and so if you get a bike fit straight away, your optimal position will be different to when your core strength has improved. I suppose it's a bit chicken and egg, because a bad fit from the outset could affect how your positioning and core strength develops. Also, 20 years makes a big difference to a human body, even if you've been riding a road bike throughout. The position that was viable then might not be now - and fashions in road bikes have changed since then too - a modern road bike might have a much more aggressive geometry.
You don't say how old you are now or what riding you have done in the last 20 years and I'd say that this will affect too - there's a difference between a 60 year old getting onto a road bike first time since they were 40, and a 40 year old getting onto one first time since they were 20.
I would say try before you buy, decide on a "type" of road bike (e.g. touring or time-trial geometry), then do some DIY bike-fitting before deciding if you want to go "pro".