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.
I don't want to be too critical of the tourist-focused shops. It is certainly possible to get a serviceable suit at one of those places that will hold up to occasional wear and fit as well as an off-the-rack suit that's been tailored for you. It can't be top quality, though, when its total cost is less than the cost of the 3 yards of quality wool required for the suit. There's been something of a spike in demand for those guys in the last 10-20 years and their prices have gone up accordingly. As a rough point of reference, the last good suit I had made there cost 1500USD.
Since most don't show a picture of the back of the shirt, also can't tell if they have split yoke. Most quality shirts will have split yoke, especially dress shirts, though it's mostly unnecessary.
One other tell of whether someone takes pride in their shirting is not using synthetic buttons.
Stitching done in Portugal is pretty good too. Of course, you can find good cheap tailors in underdeveloped countries too.
Buying quality forces you to be more conservative: that which you buy needs to look in-place (if not in-style) for many many years. You can’t buy al courant and hope it will look stylish five or ten years down the road.