Why didn't the European powers seize the Philippines from Spain?

You should look at it this way. Originally, Spain was also an old colonial power on par with the United Kingdom. Not to mention that the sun never sets, it is not bad. But the decline was too rapid. Latin American regions became independent one after another, leaving only a few palm-sized areas in the Philippines. In the end, I couldn't even hold on to this palm-sized place, so I had to retreat to my hometown.

As for the Philippines itself, the archipelago has inconvenient transportation, and the management and development costs are high based on the productivity level at that time. Not bad, but there are much better colony options on the next continent. Countries like Britain and France are all grabbing large tracts of land in India, Africa, and the Americas, and they have no time to put down their fat and take care of the three acres of land in the sea. The Americans later had no choice, so they took advantage of the war with Spain and came over to collect the spoils. This was just a springboard to strengthen their ties with the Old World. Later, the Japanese were even more afraid of poverty on the island. Once they became prosperous, they would grab whatever they could, and as long as they could intervene, they would have nothing to lose.