Here karma implies both sanchit (past life) and kriyamāNa (what you do this life).
Since very few people do such a vigorous karma in this life that it overcomes purva-sanchit, for most people varNa is birth based.
3. Varna is also linked with purushārtha.
A gruhasthāshrama Kshatriya naturally pursues (owing time purva sanskāra) artha and dharma/moksha too it good sanchit and born with that sort of inclination
Monetary status aside, all those who “enjoy life”, “dil ki suno”, “You only live once”, etc are never initiated into varNāshrama dharma and are shudra.
They have shone time and again with help of Bhakti-yoga. Either straight Mukti or good gati and then formal initiation in subsequent births
Maratha = kshatriya
Kunbi = vaishya or shudra.
Elevation of shudras/Vaishyas to Kshatriyas is common. Holkar etc are examples
While their jāti remained dhangar, varNa became Kshatriya. All contemporary dharma-pandits have certified that
That is human tendency. तमसो मा ज्योतिर्गमय.
But in era where there are material benefits to call oneself backwards, kuNbi identity became strong and Marathas too demanded and got reservation.
In era when reservation won’t matter and if dharma survives, everyone will return of earlier order.
Jāti is physical. You cannot change it. It is like skin colour. You are born with and die in your jāti
Yes due to your ancestors you will be initially accorded some respect and privileges
But if your conduct is not according to how it should be, that goes away with time/generations
Not just materially. But holistically.
If you don’t try to swim this bhavasāgara and put some efforts you are destined to drown!!