aww

The line has blurred enough for make it difficult to draw a clean line between true practical effects and special effects. Visual effects studios can and do merge real photography with digital rendering or retouching. Over 20 years ago, Andy Serkis had to don a special motion capture suit to play Gollum in the Lord of the Rings movies, but the advances since then now allow for more subtle (or less subtle) transformation of characters. The Mandalorian made extensive use of digitally rendered scenes actually projected on set so that the reflections and actor interactions feel more real in a computer-generated environment.

And of course, actual movie editing tricks have always been around, where cuts and multiple takes can create real footage presented in a fictional sequence: a single actor playing twins/doppelgangers by simply filming each side's lines separately, and then editing them together. Plus things like costume design and wardrobe, set design, props, etc.

The effectiveness of all these tricks do depend a lot on the skill and effort of the people involved, and that often means budget (including time). Rush jobs, or farming the work out to cheaper/less skilled workers, on any of these mean that corners will be cut and the end result will be less convincing, regardless of actual method.