Look youthful w/o trying too hard to look young and hip.

Yep, you can go slim fit or taper/athletic taper, particularly in the summer.....makes those clean sneakers stand out more.This is the right answer. I call it conservatively trendy. So you can still follow the fashion trends but you should be the most conservative version of it. For example a 40 year old shouldn't be wearing flare denim, but you can find jeans with a very slight/ subtle or adjustable flare at the bottom that will keep you on trend and fashionable. Another example is fitted jeans instead of skinny jeans.
Dressing age appropriate is a thing whether we want to accept it or not. Yeah, you don’t have to go dressing like Mr. Roger’s but running around dressed like Big Meech at 50+ is crazy.
Good point about staying in shape. The more fit you are the more you can get away with.
Meech dressing the way he does at 50 makes perfect sense....he literally dresses like a dude who's been locked up for 20 years.
The real issue with anchoring how you should dress so tightly to your age, is that it doesn't allow for any type of transition into anything. Just cause you hit your mid-late 30's doesn't mean you need to start dressing like a car salesman or daytime TV host.
A lot of people end up looking older than they are because of their clothing choices/hairstyles.
What people won't talk about is that is if you stay in shape, you have a far wider choice of clothing options.