Let’s look at your preference as a % of average wages.
In 1970, average gross weekly wages for men and over 21 were £28 and £14, respectively. Even if a household had two earners, which was rarer, the average weekly wage was £42 for a gross annual wage of £2184 or £182/month. Before taxes.
The average house cost about £11,500 and required a 5% deposit. Even with a big deposit you would have around a £10,000 mortgage. A15% interest rate means annual payments of £1500 or monthly payments of £125. That mortgage payment is 68.6% of the gross household pay.
Now for your modern example: Numerous online banking guides inform me that usually you can only get a mortgage for 5x household salary, let’s make it 6 to favour you.
In your example of a £300K mortgage, then, gross salary is at least £50K, monthly salary is at least £4167. At 5%, payments are approximately £15,000 per year or £1,250 per month. Mortgage payments are just under 30% of gross household pay. Less than half the 1970 example.
I do agree with you that the rental market, housing market and employment market are broken. It absolutely sucks.