As I wrote above, the proposed (!) regulation would be based on the
national housing stock. So if you are in Finnland, the energy efficiency of your house would be compared to other finish houses, not a house in Germany. Which is the definition of "considering local situations".
Also, a quick check reveals that only about 14% of the Finish population lives in rural areas [1]. Even if every single one of those persons is a house owner and poor (unlikely, as those categories are to a certain extend mutually exclusive), it would be quite feasible for the Finish government to heavily subsidize the renovation of the entirety of the rural housing stock. Nothing in the proposed regulation would keep national governments from using policy making to implement the required goals in a socially acceptable way.
Also, what do you propose would be the alternative? Improving the energy efficiency of the housing stock is in most countries among the most efficient ways to conserve energy. Other approaches to conserve energy or produce the required energy in a sustainable way cost considerably more per kw/h than bringing a 50 year old house to a modern energy standard. And of course given the prevalence of oil and natural gas based heating systems in old houses, you actually have to invest in a new heating source to switch away from CO2-emitting energy sources, anyway.
EDIT: quick back of the envelope math suggests that it would cost the finish government 5% of the current annual budget for each of the coming ten years to invest 20.000 Euros into each of the approximately 250.000 rural houses (assuming an average occupancy of 3 people per house). Not a bad investment considering that it would be made up in a few years through energy savings.
[1] https://data.worldbank.org/indicator/SP.RUR.TOTL.ZS?location...