This is true, but I do wonder if there's a way to get them to support the Taiping; they did have some supporters, and while the Taiping Rebellion was going on, they actually invaded China again.
What I've read on the European intervention in China focused mainly on the British, where a lot of the steps towards intervention come down to luck; the specific personalities assigned to the lower Yangtze, like Frederick Bruce and Admiral Hope, drummed up war outside the wishes of he Cabinet, and in Parliament there was support for the Taiping as the 'National party' of China, standing up to those venal tartars in Beijing. Thomas Taylor Meadows was a consular officer in Shanghai, and he had previously authored a book explaining peasant rebellion as the main mechanism of political change in China; to him, the Taiping were on the right side of history, and the Mandate of Heaven had ended for the Qing.
At least for the British, it's the American Civil War that makes intervention a necessity; Lincoln's blockade makes the American south inaccessible as a market, so Chinese tea the British were going to sell in America had to be dumped on the domestic market, while cotton textiles become so expensive that the Chinese won't buy them.
For the first year of overlap, though, the British strongly considered recognizing belligerent status for the Taiping; this would have made intervention against them, if not illegal, extremely immoral, while also making it legal to sell them weapons.
Li Xiucheng actually sent letters to the British consulate in Shanghai before his first attempt at taking the city, stating that he had no intention of conquering the foreign quarter, and that those buildings should raise yellow flags so his troops would know to stop. However, Frederick Bruce considered reading those letters to be a violation of British neutrality, so they were left unopened, and Li's army was repulsed by massed British and French artillery. In the short term, this won them some international sympathy, especially after the brutality of French troops got out, but in the long term, it denied them direct access to the foreigners, and much of the decision to intervene OTL was made with completely flawed information, which direct access to the Taiping might correct.
Besides the decision of the foreigners to intervene, individual points of Taiping doctrine also served to alienate possible bases of support. Hong Rengan put Confucius back on the Taiping examinations, but he was only on the scene for the last four years, so it was too late to keep from alienating the scholar-gentry that rallied to the dynasty's banner. The might also have won more peasant support had land redistribution not also come with the price of total gender separatism.
If we remove ourselves from OTL a little further, and imagine Hong Xiuquan leading a more Chinese millenarian rebellion, without the pretense of Christianity, they'd probably be much better off; most foreign opposition was based on the blasphemy of the Taiping, while their support was based on a kind of sympathy with their nationalism. Affirmation of traditional Chinese culture would have divided the scholar-gentry, and more conventional social order might have brought in even more peasants into the fledgling dynasty.