Cheap repayments don't really influence affordability of ownership, because banks won't lend more than 3.5x income. If you're earning £30k and a house in your area costs £150k, you're stuck renting unless you can somehow save a £45k deposit.
Rents have been increasing faster than inflation for many years, which is a major problem if your income is barely keeping up with inflation.
Is this what you're referring to https://www.economist.com/leaders/2018/08/09/overhaul-tax-fo... ?
Very interesting idea, especially if implemented as a progressive tax. I wonder how that would work for corporations (e.g. landlord who owns the hundreds of apartments managed through a real estate corporation). Also why only property? Why should other assets like stock holdings be excluded?
But I won't dispute that the idea seems applicable more broadly, especially since it's so much simpler and less fraud-sensitive than capital gains taxes. And while it's politically tricky, if implemented with a slow ramp up (i.e., don't do what Thatcher did) it probably won't hurt critical constituencies too bad. You could think of something like an X% tax of value above threshhold Y, and start with X low and Y high, and creep from there; e.g. X 1% and Y 500k pounds, conveniently hurting the rich not too much, and the bottom 50% of households even in london not at all. Even just the message that there's political will to do something about this would likely deflate the bubble a little.
These aren't attributes shared by stocks or other financial assets. For example it's not straightforward to charge a rent on stocks, and they're not fungible to different economic uses in the same way land is.
But in any case: Although house prices are a problem - and one UK politics feels uncomfortable addressing. You imply impure motives on the economists's side in that they're what exactly? In any case, it was the economist that suggested an annual tax based on property value, which would be a step towards a solution of that problem. But this is primarily a political problem. Extra taxes, particularly on something that is near to voters hearts and will hurt their investments, albeit in a bubble - those aren't an easy sell.
Still, while you're right that house prices are problematic, it's not reasonable to compare rising house prices to stagnant median incomes, and thus imply that housing is less affordable than previously: interest rates are extremely low, so the cost of housing is low too. The high price merely means the risk and reward of ownership is high; but low interest rate means that the amount of income you need to support a given price of housing is much lower than before. I'm not saying this is good or healthy or anything; it's just not so simple as that previously housing was affordable and now it's not.
Nor is the political problem of housing - which voters really have themselves to blame for, nobody else - any reason to ignore the employment boom. Not everything in the world is going great; what else is new? But we can still appreciate what is going well while acknowledging that other - distinct - problems exist.