Why are democratic countries like Pakistan, Turkey and Malaysia keen on a 'Pan-Islamist' dream, rather than countries like Saudi Arabia, UAE and Kuwait

Well you question has a minor problem Pakistan is not a democratic country rather it is a hybrid country. Where the absolute power resides in the hand of army not in the hand of institutions. And Countries like Pakistan Mahtir led Malaysia and Turkey keen on pan Islamist because they want to replace the hegemony of Saudi Arabia and its allies in the Islamic world.

After Mahtir mohammad resignation as PM of Malaysia the stance of Malaysia shifted. They are now not interested in that group. And the stance of Pakistan and Turkey is totally based on the economic geopolitical situation.

After the purchase of S-400 from Russia USA put sanctions on Turkey by the CAATSA act which make Turkey angry. And as USA selling weapons to Saudi the power balance of the region may get changed so to counter the influence of USA Turkey start targeting USA’s ally Saudi Arabia by putting a idea of neo-muslim world where the power resides in the ottoman region of the past.

Pakistan supported the act of Turkey because of multiple reason the first one is growing economic ties between Arab world (esp Saudi arabia ,UAE ,Oman ) and India second reason is of USA China tension. Pakistan was in verge of choosing any party and they choose China because China’s relation with India at its low after 1962 because of galwan valley clash. Also India and USA are now strategic allies so pakistan can’t trust USA or its ally Saudi so they join the invitation of Turkey.

One of the reason is of defence also as Turkey and Pakistan have agreed on the sale of a batch of 30 Turkish-made T129 ATAK multirole combat helicopters. Pakistan as a country mostly import weapons from other countries but because of Indian diplomacy many countries cancelled the orders placed by pakistan.