Instead of using the term, "bash", I would recommend changing the title to "manufacturing education" (or similar term), unless there is a preference to bait PinSide trolls for useless responses.
The facts do already exist for those that have watched the industry.
Reading for education, and a basic explanation.
This general subject area has already been discussed in this forum, other forums (innumerably), and other forms of social media.
This is not a particular complete "mystery" regarding reliability, serviceability, and durability of older titles made by previous manufacturers by companies such as Bally, Williams, and Gottlieb by conducting proper electronic and physical comparisons of all aspects of the games and manufacturers themselves. These terms I use, the "RSD" of pinball per say, as they are not all equal. However, there are examples of pinball manufacturers game designs that just were outright BAD. Playmatic and Mr Game come to mind. Unfortunately, and not to sound slighted, Stern games have never been built to the level of quality ever in comparison to BLY/WMS since 1977. All experienced operators know.
Remember specific titles are also important for purposes of "robustness" as some titles were better built in design than others historically on areas such as board sets, materials, or things such as playfield ramps, and not entirely based on heavy play on routes.
Simple examples would GTB SS80 games compared to early Bally (edge connectors, ground problems, power supplies), Bally-Midway games of the mid 1980s in comparison to Bally games made from 1979-1982 for areas such as cabinets (particle board materials as used in arcade games), Capcom board sets from 1995-1996 to BLY/WMS games of the same years (power board capacitor failures and some fusing problems), AGC cabinets in the early 90s comparative to BLY/WMS (poor silkscreening), or games made from BLY/WMS 1990-1999 in comparison to Stern games made from 1999-2009 (features and artwork simplifications).
Discussions exist of comparison of games made from Stern in 2011 and then fast forwarded to 2015 (solid state SMD electronics, and changes in CC formula, EPA standards, application thickness, application period, ink screening periods, wood drying, and curing).
This means other manufacturers also tried various "cost cutting" methods as well in the past, such as electronic components, connectors, socketing, fusing, power regulation, displays, cabinet making, and playfield composition especially when markets were harsh, not growing, which is an indication of winds of change in its own right. Stern is not unique here.
The comparisons in "passage of time" do exist for those that do wish to learn.
Some changes slipped by, some did not, some were not accepted readily or at all, but that was all in comparison to operators that reported them for reliability or durability concerns, not the growing number private owners that may not understand (or care) regarding the coin operated industry.
Some specific games have been discussed in extraordinary detail.
Overall, there are just too many topics listed in your initial thread post to cover in an individual response.
However, many older collectors, operators, and technicians have already made our final decisions governing present changes by Stern, namely stating:
"Stern will continue to construct easier to manufacture games to ensure maximum short term profits based on the market requirements with no significant concern for the future of the titles beyond 10 years of operation and reduce basic features that will be accepted or unnoticed by the private consumer."
This could have been quoted almost directly by Stern investment council around 2007.
This has never really been different in their business model since the the early 2000s. They are not JJP. I know this sounds extremely rough, but this is the reality. The only real difference is the prices kept rising unnecessarily since 2011, and the quality reversed. This is easy comparison when you sit a TSPP next to a SWLE or BM66SLE. It is a very bad joke. This is despite no one actually coming out a saying these direct words, including distributors. Stern "upped" the cabinet construction reinforcement recently (2017), because they had to, based on complaints. They simply could not avoid the controversy. Some current games may not last 5 years for full functionality of board failures. Stern continues build, outsource, and diversify their company to increase profits in expanding foreign markets and provide a potential cushion against economic recession in the United States and survive again in the future. They learned from their mistakes of the past.
This process "cost cutting" occurred long before the last two years of the SPIKE introduction, if an owner was observing.
Granted, games were never necessarily designed to last 20-30 years, but if cared for properly, and built well to COMMERCIAL STANDARDS, they do, as I can attest from games I own that are well over 50 years old.
This mindset is not being applied to Stern's present games for construction, but akin to disposal consumer electronics, not commercial devices. We are only about two steps away from having the coin door removed, coin mechs are already an "option" for some other manufacturers, and was already tried with Stern's home edition game, "The Pin".
In summary it is the term, "paying more for less" (now nearly double or more in certain cases for reduxed playfield designs) which was a result of several major market changes which occurred since 2011, but particularly not only the resurgence of interest in pinball (again) and the introduction of JJP as a potential competitor which eventually materialized in 2013.
If all this is acceptable to some, so be it, but that does not mean I have to agree as "old" collector.
If Stern wants to reduce the quality of the their games, the prices have to return to at least equitable operator level.
This is only a recent "revelation" to some, and something I and others continue to watch from a distance as we "bowed out" long before the tidal wave begins to slowly crash over the market surf that has already started as prices have begun to peak.
If you have not already watched this very specific video, this is a good start for additional education without creating further controversy or responses of denial by owners that may have just joined the pinball hobby in the past 7 years.
I would recommend you also read the comments BELOW this video for additional areas of changes of people that actually have conducted research and observations, not general enthusiast opinions.
A decision can then be better determined by an individual, the consumer, of what constitutes a proper "value for cost" and how the games will actually hold up in the long term.
If there are additional questions, you may contact me or I can redirect to others.