Looking at the mill for a fabric can be helpful, especially for wools. Mills such as Holland & Sherry and Scabal have built a reputation for quality fabrics though they're generally not household names so they do not yet have the motivation to go down-market to increase their sales (unlike Zegna which has become semi-famous and now makes some lower quality fabrics). That said, you won't find their fabrics except on top-tier off-the-shelf clothes or custom clothes.

If by stitching you mean construction quality, you can certainly find that in many places. For suits, England and Italy are famous for it though both places do have lesser-quality vendors who will happily trade on their country's reputations and take your money. I had most of my business clothing custom-made in Hong Kong where the tailors learned from the Brits but are still much less expensive. You have to be careful there, though, because there are lots of guys who prey on the tourist who has heard that cheap custom suits can be had in HK but isn't able to assess quality.

++ on buying conservatively-styled clothes. I'm in my 40s and still wear the suits I bought in my 20s and hope I'll still fit into them in my 60s.