Now with a newborn, I don�t have as much time to spend with him as I would like. A lot of time, he would just lay on the couch until I suggest something fun/challenging to do (e.g. new puzzles, snip circuits, mazes, books, etc).
Rather seeing the lack of ability to self entertain a reason to have more electronics, I would suggest instead it is a reason to have less. Learning to self engage, handle frustration, handle boredom, enjoy day dreaming, etc. are all important life skills and the development of those skills can be interfered with by ready access to electronics. Consuming electronics isn't a hard fought skill, the games and software are designed to keep the child attentive and pressing next. It is at the very core a passive activity.
While I don't at all think preschool is mandatory, interacting with the world is. For a preschooler that can be stuff like: going to the post office, taking walks, going to the park, going to library story time, etc.
While he needs your attention he doesn't always need your full attention. It is appropriate to expect preschoolers to handle some divided attention (like you are feeding the baby while semi paying attention to him while he builds with trains or whatever). Also, not everything needs to be a child centered entertainment activity. He can help make sandwiches, help wipe off the table, etc.