Likely this is one of those things where "beauty is in the eye of the beholder".
Everyone is subject to their own bias, the effect of well designed marketing, and the amplification of that marketing by current owners of that which has been marketed well. This is common in all market segments but seems especially common in the marine world. I am aware of my own bias.
This boat will likely close at around 100K US or about 90K Euro. That is not much money for a lot of boat. If this 34 year old boat is as it appears in this ad, think about the condition that the hull and house are in compared to most mid eighties KK 42. Now think about what each of those boats might look like in another 20 years and how much money and intervention it will take to survive those additional 20 years.
I get that it is a metal boat in a plastic market. That must be considered if resale is an important part of the equation.
But, if long term cruising with a very moderate cost of ownership and maintenance is the goal, this boat wins hands down for me under the conditions that 99+% of us will cruise. This boat looks strikingly easy and inexpensive to maintain.
Given what I see in the weld on the center girder, the welds on the gussets of the rudder tube do not concern me unless they concern a good surveyor. With 1000 hours of sea time so far and no apparent problem, and with the gussets being a secondary means of stabilizing the tube, I am not getting heartburn about those welds.
To highlight the first observation that beauty is in the eye of the beholder and their bias, here is mine: If someone offered me a mid 80s KK42 for X$ and this boat for $100K more (the entire asking price), I would take this one. And that considers the fact that I think a mid 80s KK42 is a helluva boat.
This is a well conceived boat that appears to be in great shape and stands a good chance of staying that way for a VERY long time. At this price, that seems like a very good deal.
If you will need to sell it next year, I would not touch it. The sentiment so far on this forum stands as exhibit A in that regard. That bias, however, is what will provide someone the opportunity to own and cruise a very nice boat for very little money.