I remember back when I made the transition from part-time hobbyist pursuing his ancestry to hard-core genealogist, that I attended several lectures by noted genealogists, many of whom became my friends, about how to take that next step in research. Mind you, this was back in the day, i.e. no Internet. Practically no computers. I learned deed research. Probate research--not just wills, but guardianship papers and administration papers. I learned about all the sources most people never used outside of birth, marriage, and death records. I thought and believed that if you just worked hard enough and sought out all these records, you would make the necessary breakthroughs to continue your research.
I understand now how much bullshit that all was. They should have included a class that said: Someday you will not be able to prove your ancestry beyond a certain point. And then comes the day when all your ancestors are either fully-researched or blocked. Those that are blocked will always be blocked. At this point you need to either (a) find a new hobby; (b) become a professional genealogist and do other people's genealogy. And, indeed, those who are truly hooked move on to do their spouse's ancestry; their in-laws; their neighbors, their pets, etc. I can see why people move on to medieval genealogy as well. One or two good gateway ancestors can lead to several more hundred years' worth of ancestry and research that is still yours.
But what can we honestly expect? I've long suspected that Jacobus and his entire generation of genealogists got off scott free. All they had to do was correct the worst genealogical errors of the preceding generation, which were legion. It doesn't take much effort to turn an F paper into a C+ paper. Even if most of the Jacobus/Davis/Holman, etc. researchers rank at B grade work, it still doesn't let them off the hook, that they took the lowest hanging fruit for genealogy and published it. When I look at what I know about my own ancestry and the lines that are already in print, it is largely those three and some others that did it all. So, if they hadn't done that, I would be making discovery after discovery using deeds and probates. I don't because they already did it.
So, I'm stuck with these brick walls. And I really thought, on the whole, it was just that these families were either un-researched or under-researched. However, I've come to the conclusion that there just are no records to adequately prove the relationships. You can guess. You can make elaborate preponderance of the evidence arguments. But you can't prove by standard genealogical principles the relationships. Therefore, you can't either join lineage organizations or you can't move on (with a clear conscience). You're stuck. Forever.
I guess the argument can be made that there is always something new, even within your own family, to research. I can put down all my 18th and 19th century brick walls forever and concentrate on other things such as English origins of 17th century immigrants. However, it galls me to do so. There is something highly unsatisfactory about leaving behind a problem in 1814 to pursue a 1610 problem.
I just hate wasting my time. And energy. There should be some sort of (*) by the names of people that can never be solved.