Landscape design and gardening trends change like every other sort of fashion. Several fads of the past were quite practical and justifiable. Many were not.
Whether justifiable or not, many merely became old fashioned. Some evolved into a more contemporary style. Others were not so adaptable. Planning for a landscape is easier than planning for fads.
For example, plants seem to be disproportionately small within a new landscape. That is because someone planned for them to have sufficient room to grow.