Generally there is always a large influx after patent protection expires; and quality can go both ways.
Probably the best and most well known example of this is the Honda Monkey engine. Honda still makes theirs, Lifan makes a low end version and Takegawa makes ultra high end versions that are competition ready.
I all truthfulness; it is generally not the manufacturer's fault, it's the dubious and inaccurate claims made by random sellers about certain products. Low end products are typically the scrap or production overruns that were never finished.
In the last few years there have definitely been a few companies trying to build revenue on expired designs. Actually, if my memory is working, that is how Echo established and built themselves up. Occasionally these types of companies will buy the old molds and fixtures but it takes a few years for them to figure out the QA processes.
As for your question specifically, in aftermarket pistons most recommend meteor if OEM are not available. In rare cases you might find a Wiseco match.