I’d say go with your impulse and start with Matt Smith’s first season. It’s a great jumping on point, while very much being season 5 of an ongoing show. Viewers were introduced to the new Doctor through a child’s eyes (I’m simplifying here to avoid spoilers), and it gives a new sense of wonder to the drip fed lore references throughout.

Because of the show’s history you could more or less start with any new Doctor, but for new viewers in 2025 I believe the Smith years* are a good starting point.

Others will recommend you begin with the 2005 revival but IMO those first seasons can look a little janky by current standards. There are seminal stories there that you absolutely must watch, but the visuals level up a bit when showrunner Steven Moffat take over and Matt Smith becomes the Doctor.

* or “era” as Who fans somewhat arbitrarily call any actor, writer, and/or producer’s run on the show. Some fans get very uptight about terminology (like insisting that only classic Who has “seasons” and everything post-1989 must be called “series” instead) but don’t pay any serious attention to them 😆