That wasn't the first instance of foreign countries building some plants in China, or even the Chinese building their own plants. None of these limited, state-focused attempts, including the 5 year plans, resulted in any significant change in China's economic structure.
Yes, it was not the first time foreign countries building up plants in China, but it was the first time a major power builds plants
for China, teaches China how to use them and lets China own the plants, and on very favourable terms.
No, the early five-year plans had extremely important effect of China's economy and politics, especially the first two of them.
You wouldn't have said that if you know more about the first two plans and the aid from USSR. Here are what I can find from the books:
During the first five-year plans, the following plants began construction as a result of USSR aid:
25 for coal mining and processing, capacity 21.65 million tonnes mining, 9.5 million tonnes washing;
2 for oil refining, capacity 1.7 million tonnes;
25 for power generation, capacity 288.65m kW;
7 for steel, capacity iron 6.7 million tonnes, crude steel 6.366 million tonnes, steel 3.6 million tonnes;*
11 for rare metals, capacity varied, including Al, Mo, Ti, V, Mg, W, Cu, Sn;
7 for chemicals, capacity 0.154 million tonnes synthetic ammonia, 0.188 million tonnes nitrate ammonium, as well as other chemicals;
24 for heavy machinery, basically covered the needs of the aforementioned plants, as well as machine tools, motor vehicles, tractors;
1 for light industry, capacity 50 thousand tonnes bags for concrete and 60 thousand sq. m copper mesh;
2 for medicine, capacity 115 tonnes of antibiotics, China no longer needed to rely on import;
and most importantly, 45 for
military industry.
*: In comparison, before 1939, the production capacity for steel under Nationalist Governments control before 1939 was 40 thousand tonnes, whereas Japan had 5.8 million toones and US over 80 million tonnes.
As for the second five-year plan, well, it was, and still is, blamed for that well known famine.