pistons yes, hyper-eutectic alloys and better skirt designs. Certainly pistons are better and cheaper than ever before, thanks to high speed machining with PCD inserts.
bearings, overall....no Some do run tighter but many don't.
there have always been some engine built to very tight specs and others not.
In some cases it seems to have little relation to how much people like them or don't.
The average engine today.... Not really any more precise than was achieved 50-60 years ago in better examples.
Better designs, better oil, better fuel, better fuel systems, better air filters, better materials.....is what makes them live so much longer.