At primary school, call it mid 60s, we recited our prayers and then a series of rote-learned calculations as the teacher did a series of necessary but non-teaching tasks eg resolving dinner money (for a class of 40)
These became more complex as we got older, and eventually included times tables up to 13 times, then helpful info on how many chains make a furlong. Educational theory having advanced, rods, poles and perches were omitted.
Being slightly discalculic I still have to quickly run through from the beginning to get to 7x9. Bearing in mind that for me the imprinted sequence begins 'hail Mary full of grace'. Not exactly lightning speed but it's all there eventually awaiting recall.
In the later 1960s academics pointed out the need for problem-solving skills and the need for mathematics to be taught not just as doing sums. A secondary schools syllabus was introduced called 'The School Maths Project' (SMP) which taught all sorts of areas of maths that had were previously only encountered at 18-plus. The thinking behind this was that as technology was changing different skills would be necessary, whereas mechanical skills (calculation) would probably be increasingly automated. This was driven by the universities of the time. It was a clever project in the right hands, but it assumed the pupils had already memorised their tables. The problem was that it was taught to a generation of new teachers who entered primary schools and hadn't been taught the need to teach by rote. In fact as others have hinted, teaching by rote was considered 'a bad thing' by the late 1960s.
This coincided with other changes in educational theory, some of which were disastrous - or at least, which were interpreted and applied in a disastrous fashion. In my direct experience for example a secondary school in Leicestershire did not require pupils to attend lessons. BTW there have been private fee-paying schools since the 1920s that ran on these lines, and which were the models for individual pupil-centred learning.
Similar issues that have affected maths learning have affected literacy skills.
Part of the reason for educational theories going teats up was that after the last Wilson government state educational became a political football, with politicians of right and left using schools as a means of forwarding their own individual careers first, and their parties' public profiles second.
One function of this was that educational funding became increasingly short term. There isn't one round of schools' funding over the last 20 years that has been for more than a 3-year spell. So short-term funding is thrown at a long-term problem.
The nation needs an adult in-depth discussion of what 21st century education should comprise, but instead we get knee-jerk reactions and a desire to blame.