Ustadz, lately I've been having doubts about missing pillars or obligations in wudu and salah, such as whether water reached a certain part, whether I recited al-Fatihah, which sujood I'm on, or whether I did the takbirat al-intiqal. Should I ignore these doubts? When should I take it seriously?

Ustadh AbdulAziz al-Haqqan

You should ignore them, as it is very evident that this is waswas.