I'm not sure this is a fully-qualified answer, but let me take just one example I'm reasonably familiar with.
This may qualify as a rant ... sorry ;-)
I own an original Japanese Squier '57 Strat, which I've had from new [mid 80's] & a Squier Anniversary Strat [can't remember which anniversary, sometime late 90's or so, & the guitar is currently in storage so can't look up the details] There's also a mid-90's 'big headstock' Squire somewhere in storage, which I've never played much so I'm not using it in this comparison.
For true comparison I also used to own a real Fender '64 Strat, a good one, daphne blue. It's now in the hands of one of my best & longest-known friends, so it's not lost forever.
In order of 'how good they really are' - the '64 was quite clearly the best, though not by far if you were just listening, rather than playing. The '57 Squier doesn't quite have the same sound, it's a little more muted, but it's a varnished maple neck & my Fender '64 was a rosewood. I'd call that 'model variance' rather than true quality difference, if you are only listening. The Squire doesn't feel quite as spry as the '64, nor does it have the body resonance - but it's really pretty darn good overall.
The Anniversary, on the other hand, sounds & feels like it was made of plasticine. It has no resonance, no feel. To all intents & purposes it's the same as the '57... but it isn't. It's heavier, feels 'fatter' & not in a good way - & the 57 is already twice the weight of the real '64. The '64 is light & agile & resonant. It sings. You can play Beach Boys, Hendrix or early SRV on it with no sense of irony. The anniversary on the other hand is a lump of lead, physically & sonically. It needs a great amp to even sound average.
...and that's before we get to the real entry level ones you find in toy shops as well as the less salubrious music stores.
I had the unfortunate job of going round a major toy retailer a few years ago, installing their shop-floor demo models of the newest 'entry-level' Squiers [& others even cheaper, which I can't even remember the makers]. They were going to be retailing at around £150. My Japanese '57 cost me approx 250 new in the 80's, so something has to have slipped somewhere.
Warning - don't play one of the new ones without gloves - they will take your fingers off. The frets are so badly finished that you are in real danger of cutting yourself if you slide up the neck without proper care. They were probably made in a high humidity environment, then shipped to average humidity Europe [in my case] with no care for the potential shrinkage whatsoever. I'd guess they aged the wood they were made of until the leaves fell off, not much more .
The action as supplied is 'not at all set up'. Nothing, in fact, is set up - & bear in mind the target customer for these wouldn't know what a setup was if you hit them with one - so that's not acceptable, imnsho.
Honestly, the cheapest of cheap guitars you could get for £25 from Woolworth's in the 70s were better-made. They were utter cr*p & sounded appalling, but they were better-made.