It is certainly true that the level of Martian technology is far below what it once was. Even the means of making the canals so long ago, surely their greatest achievement, is wreathed in legend myth and folklore. If any Martian knows or understands how it was done, then they are not telling the Earthmen.
As a society they also suffer from a lack of resources. Fossil fuels were exhausted long ago - coal-burning came as a surprise to this generation of Canal Martians. Iron ore is abundant – this is the red planet after all – but it is difficult to turn it into good quality iron or steel in any quantity for two reasons. Firstly, the thinner air on Mars, with its lower oxygen levels, makes it difficult to achieve the temperatures needed to smelt iron. Secondly, the general shortage of fuel means that it becomes an economic and environmental impossibility to feed any large-scale production. Iron and steel are made, but Martians have gone back to small-scale production and use alternative materials wherever possible. In part they use softer metals, such a copper and tin, but these minerals are also in relatively short supply and so a great deal of recycling takes place. But Martian society has also developed the use of plant materials – and other renewable resources – to replace metals in many areas of life.
Canal Martians cultivate a great many crops that have been bred for very specific reasons other than for food. Some are for straightforward uses such as coloured dyes and cloth (similar to cotton and linen/flax). But many more are quite different form any earthly forms. Presumably these have been selectively bred from now-extinct species to meet specific requirements.
They have a plant very similar to bamboo, “Jee-oo”, but which is far stronger when treated. It has a resistance to deformation that makes it very valuable as building frames, scaffolding, fencing, and even as weapon barrels. When split and treated it can be moulded into extremely hard plates.
Another plant with a much spongier interior, is also used in construction. This “Betaan” is mashed and left to break down in water for several weeks. It is then mixed with sands with a high iron content to create a substance similar to concrete when dry. In its liquid form it can be poured into moulds or forms to create beams and panels.