As with most things, I would imagine it depends on your level of competency.

For a competent DIYer, changing the oil, oil filter, air filter etc. are very easy. (And I'm happy do this for our cars).

On my 1997 Landcruiser or 2001 Yaris these are things even a novice/beginner could tackle.

However, most modern cars have many sensors and electronics which require sophisticated diagnostic tools - and not always available to the casual DIYer.

Even something relatively simple like changing the battery, requires it to be "re-coded" to the car.