A very good question, actually, and one which gets to the heart of materials science. Which is nowhere near my areas of expertise, though I've been looking into this incidental to other interests.

Meta-answering by way of what the pre-plastic world looked like....

The history of the study itself is interesting: materials science & engineering grew mostly out of mining engineering, which subsumed metallurgy (see Agricola's De Re Metalica, still a leading text through the early 20th century, or the evolution of M.I.T.'s course catalogue), but picked up other elements (so to speak) especially with the rise of coal-tar and petroleum (organic) chemistry. There was the golden age of plastics, roughly 1920-1940, when many modern polymers were invented (polystyrene, polyester, PVC, Nylon, etc.). Earlier, ~1840s-1890s rayon and celluloid (from plant fibres) and bakelite (coal tar).

Vaclav Smil has an excellent book on materials, Making the Modern World, which looks at sourcing and usage (https://www.worldcat.org/title/making-the-modern-world/oclc/...). Strongly recommended.

You can look at what materials were used before plastics were available. Early 20th century children's toys were often made of stamped tin. Wood, woven fibres or reeds (baskets, wicker or rattan furniture), fabrics, hides, metals, and stone, were commonly used. Plastics replaced many of these on the basis of cost, weight, flexibility, mouldability, process-scalability, automation, and frequently durability, as well as water-, air-, and rot-resistance.

Human use of materials gives a strong sense of time. In film and theatre, much of the atmosphere of an era, beyond mere styling, derives from the materials used or incorporated: stone, brick, plaster, ceramics, wood, fibres, dyes, glass, metals, and synthetics. Mid-century US clothing is dominated by wool and leather, the 1960s mood is set by synthetcs and plastics, 1970s by polyester. Since then there's been a movement back to more natural fabrics generally, though nylon outerwear cold-weather garments are still popular.

Many of the shifts in material use are energy-bounded. Not merely in processing (metals smelting, glass and ceramics production), but in transport and sourcing. Paris's catacombs, I've just learned, were largely formed as quarries for building materials. Almost all pre-modern construction used locally-sourced materials, or materials which could be moved nearly entirely by water, with minimal thermal processing.

Lumber use was historically minimised due to its scarcity -- half-timbered and full-brick or stone construction limit wood use for a few weight-bearing members, and fill planes and voids with more-abundant materials -- stone, wattle-and-daub, lathe-and-plaster, brick, even straw. (Fire risk was another consideration restricting wood construction in pre-modern cities.) Whilst the US had vast forests at its founding, they were largely consumed within about a century, for both construction and fuel. Despite its coal riches, wood use exceeded coal through the 1880s. (Oil surpassed coal only in the 1950s.)

With coal, steam, rail, excavators, drilling rigs, pipelines, and tankers, sourcing vast amounts of coal and oil from inconvenient remote locations and synthesizing useful fabrication and construction materials became possibe. Voila: Plastic age. Metal mining, refining, smelting, and founding also advanced rapidly -- highly-reliable, high-power locomotives, rails, pipelines, and steamships were infeasible prior to Bessemer steel (1860s). Aircraft required aluminium structural members and fuselage panels (1880s). So there's a complex bootstrap process involved.

(This isn't a defence of plastics, just a brief, very rough, and non-expert materials/economic history.)