technology improves over time (I am talking in an RPG way here).
if i was looking at a competitive PvP game like counterstrike then i would feel differently. there balance is vital, but imo in an RPG it is ok for a little creep.
I'm not sure what you mean by 'an RPG way' here, or what would make balance less important in an RPG.
Newer cars are more efficient, have better use of cargo space and are safer too...
They are, but I don't see any particular reason why the current automobile trends should be extrapolated into far future fantasy spacecraft. There are plenty of real-world counter analogies too. We have aircraft using seventy year old airframes that haven't been decisively surpassed and the hull forms of displacement vessels (larger ships and submarines) have not evolved dramatically in a similar amount of time.
The Elite setting is one in which spacecraft have been mature technology for several centuries. Not only that, they are highly modular, so advancements that don't apply to the hull/spaceframe itself are tied to modules and can be ported over that way.
Mamba pitch rates could be better, but I highly doubt if they ever adjust these rates as they never did that with any ship
Python had it's rotational rates severely nerfed in 1.1. FDL had it's rotational rates increased significantly in 1.5. Mamba had a it's rotational rates increased significantly in the beta in which it was introduced.
FDL until 2016 orginally had a one size smaller powerplant as well (it was even mentioned in galnet when they upped it), as it had size 5, and much better heat disspation at some point (before plant buff)
The FDL buff in 1.5/2.0 that increased it's PP size also increased it's pitch rate by 15% and it's roll rate by 10%, as well as a second buff to it's thermal efficiency.