They can be. I have a few Seiko 5's that perform much better than the OP's, but I service them myself. And I had a Seagull that was decent, but didn't last more than 5 years without structural failure. It is the material that is critical. Russian movts have also suffered from this. This is not to say all Russian watches are bad, or even all Seikos are bad. They are what they are, affordable decent quality watches. I have a Cardinal with a Russian movt, and it runs extremely well and seems to be made with good quality metals. If you were to take a Segull or Seiko or any mechanical movt, it can be tweaked to run quite well, but final fine adjusting and tolerances for these watches at the factory are not the same as say, a Swiss maker's similar product. I have come across Omegas that were pretty bad, design wise, and suffer from horrible errors, regardless of tweaking, and I don't mean vintage ones either. But these are the exception. A good example is the Rolex 3100 series movts: Excellent materials, several design flaws. The rotor will eventually hit the balance while being shocked. There is an extra bridge of metal to protect the balance because of this. I say why not fix the rotor post problem? It has actually gotten worse, as the new posts are smaller.
But I digress.
There is an inherent danger in pointing at particular brands and trying to assess their quality level as a whole, it really must be done carefully. Seikos are designed well, and are durable, and have many excellent case designs. Their quartzes, in particular, are very good. Have you ever seen an ETA 805 series? Complete garbage. You will find these in $300 Swiss quartz watches. My Seiko Panda has a vertical clutch column wheel movt, and from that standpoint, is a good design. It suffers from poor materials, however, and Vintage Seiko parts aren't easy to come by. A good watchmaker can adjust one to run quite acceptably, and this can be said for most mechanical watches when they are new.
So I wouldn't say they were worse, in fact, I have a soft spot for Seikos and on my own personal scale, I like them better than Seagulls. But I'm the guy that has to crawl inside the movt and really assess what it is and what it's doing, so my point of view is somewhat different. For many ppl, Seiko mechanicals have the warm and fuzzy factor, they seem to last forever, and everybody knows them and probably has owned one or known someone in the family who did. And while you might think it pedantic for someone to rage about a broken screw because of quality, it speaks volumes about cost cutting measures in the watch. I recently had a customer's Longines Railroad watch, and what struck me first as I serviced it, were the screws: They were flawless and of such high quality, they were the standard on which the watch was built, with it's perlage and decoration even in places you wouldn't see it. The only other time I was so impressed with screws was in a Patek.
So, Seiko good, Seagull bad, or vice versa? I'd say they were comparable, but Seiko has invested a lot more as a company, and been around a long time. It's got brand recognition, and they have had a lot of years to experiment with their movts. Again, if you have a watch that seems like it's not performing, take it back under warranty by all means, or if not, get to know your local watchmaker and have it tweaked.