I completely agree with the original poster and have been in a similar situation, working in drug discovery for over 20 years. I changed careers and got a PhD at the tender age of 43 to get into biomedical research because I felt most researchers are not open to new ideas, taking a genetics-based approach to everything and don't realize the shortcomings of their approach and how narrow their focus is. For example, mice are used in most AD research, but mice lack the Alu elements found in humans (> 1 million copies in the human genome). Alu elements are believed to be involved in 37 neurological and neurodegenerative disorders including AD. So, you would think researchers would question the basic value of using mice in their own research with all the shortcomings of mice. Also, although the human and mouse X chromosomes have many similar genes, the overall structures are different, causing differences in the higher-level epigenetics in the mouse and human Xs. Fortunately, human brain organoid techniques are improving as a potential alternative in AD research.
I think epigenetics (control of gene expression) is of great importance in understanding AD and provides a multi-gene scenario. For years I was interested in lupus primarily and only started looking at AD about 2-3 years ago. I was amazed at the similarities. In fact, I recently published a hypothesis that can explain a possible route to AD based on ideas I had previously published on lupus. I developed the AD hypothesis based on a systems biology approach (rather than a narrow reductionist approach looking only at tau, amyloid-beta, or ApoE4) and based on autoimmune disease tautology. AD is a neurodegenerative AND autoimmune disease and AD has many aspects common to other autoimmune diseases. In fact, 25% of autoimmune patients have more than one autoimmune disease, of which AD can be one of them. Researchers become too narrowly focused on one disease and fail to gain insights from research on other diseases. The hypothesis is built around the nucleolus, a major epigenetic structure in cells. When the nucleolus is overly stressed it can expand and disrupt peri-nucleolar chromatin thereby disturbing epigenetic control including genes in the nucleolar heterochromatic shell and neighboring chromosomes such as tau on chromosome 17, presinilin-1 on chromosome 14, amyloid precursor protein on chromosome 21, and ApoE4 on chromosome 19. Chromosomes 14 and 21 are part of the nucleolar shell, chromosomes 17 and 19 are involved in DNA repair, a function of the nucleolus, and the inactive X chromosome (Xi, aka the "nucleolar satellite"😉 has important sequestered gene alleles that could be problematic if opened to expression. I should note that chromosomes 17, 19, 22 and Xi have very high concentrations of Alu elements. Expression of Alu elements can disrupt nucleolar integrity, even fragmenting nucleoli. It should also be noted that many autoantigens in lupus and other autoimmune diseases are at least transiently nucleolar components.
The hypothesis was published over a month ago in Journal of Alzheimer's Disease (DOI: 10.3233/JAD-231184) and has only about 43 reads so far. I am hoping to get some feedback (pro or con) but haven't heard anything yet. It also has some ideas of experimental and therapeutic approaches for the ideas. I might try presenting the AD ideas at a conference, but a 10-15 minute time slot would be way too short for such a complicated "alternative" topic.
I hope this line of discussion continues since I think there is a long way to go to get the research community out of a genetics-based mindset and open to epigenetics. Cancer research has always had a genetics mindset but recently the concept of some cancers arising from primarily epigenetic disruption rather than genetic mutations is being discussed.