There were multiple reasons for opposition to modernization.

One of the key ones is that modernization usually involves lots of changes happening in a short period of time, which in turn usually threatens the entrenched interests of certain groups in society and government. An example of this would be the Samurai in Japan: the Meiji regime which carried out modernization realized the need to cut the rice stipend which was paid out to Samurais because it was taking up 1/3 of the national budget. This in turn contributed to Saigo's rebellion which had to be crushed by armed force because Samurais who lost out on what amounted to welfare payments were angry.

How could implementing obviously more effective military tactics be unsuccessful and controversial in a country?

I don't think they were at least in Japan and China, both countries built up relatively modern military forces by the late 19th century (the Beiyang army in China and the IJA in Japan). In China this was at least partially because the natural institution for opposing those reforms: the Manchu bannermen, were largely destroyed by the Taiping rebellion and alternative military institutions rose to replace them.

In the Ottoman empire this did provoke a rebellion, because the "new army" created by the Sultan meant resources were to be diverted from the old system to the new. And that on the long run the creation of an army on the European model meant even the fiction that the Janissary were still an effective military force could not be maintained.

The same goes for industrialising the economy.

This isn't something unique to non-western countries either, even in England you had the Luddites who smashed industrial machinery because they saw it as taking jobs away from them.

Industrialization tend to initially harm a lot of people in the economy. Railroads for instance renders porters, teamsters and canal workers jobless which in turn creates a lot of discontent directed against the government. This goes double if they are foreign owned. At the same time there's limited resources at any given of time for capital investment. A government which fears for stability of the country might very well decide, quite rationally, against building a lot of railroads in favor of other projects.

The rise of new economic institutions and power also naturally meant that power tend to shift away from traditional economic elites. Building a new port for example would divert trade and revenue from the owners of the "old port". This meant in some circumstances the existing elite (and I can cite examples of this) actively sabotaged economic progress to preserve their own interests (this was a big issue in parts of 19th century Latin America).

I think one of the best things one could do is really to examine the modernization efforts of the 19th century and start comparing them to that of the 20th century. An interesting question would be if a 19th century Chinese Mandarin which opposed modernization is all that different from a Soviet bureaucrat who opposed market reforms in the 1980s.