I'm on mobile and a Pacific Ocean (and North American continent) away from my computer so this will be a quick answer.

As I'm sure you know from your research, the Boshin Wars were fought between Tokugawa Loyalists and daimyos who hoped to restore power to the imperial house (mainly the satsuma and chosu domains). The daimyo had a number of reasons to be upset with the Tokugawa house, among other things, they had been excluded from the political process for the past 200 years (because they supported Toyotomi over Tokugawa at the Battle of Sekigahara in 1600) but the final straw that caused the revolt against the shogunate was the handling of the west after Matthew Perry's arrival by the Tokugawa shogunate.

A number of unequal trade treaties had been forced on Japan and Japan was generally being kicked around by the west. The Tokugawa shogunate had made limited efforts to modernize the country and protect it from western intervention but had mostly failed to make meaningful progress in defending the country. The shogunate a legitimacy was based on its ability to defend the country militarily so this was obviously bad for its future.

The Imperial Loyalists (who eventually won)hoped to secure the independence of japan from the west and part of this was westernizing. This was similar to what many other countries in Asia did, such as China's self strengthening. However Unlike china or other Asian countries, the Japanese were willing to adopt all aspects of European society in order to compete. After the Iwakura mission (a tour around Europe and America by high ranking members if the Meiji government) Japan realized that the West's advantage came not only from technology but from industrialization, transparent government and free trade. Merely adopting western technology would not bring japan to parity with the west, the whole country needed to be overhauled. Another motto of the Meiji government, that perhaps better exemplifies their objectives, was "Western technology, japanese spirit." It's important To note that japan did nt want to become a western country, only to reach parity with Them and they felt the adoption of all western institutions and culture to be necessary for this.

Tl;dr: Imperial loyalists had a lot f reasons to dislike the Tokugawa shogunate and their poor defense against the west was merely the straw the broke the camels back. The Meiji governments westernization programs were an effort to secure Japan's independence against the west.