50% time is somewhat easier, though it's unclear as to what extent you can furnish your career on that. 80% research time is harder--issue is more or less how much pay cut you want to take. Institutions would happily take you on by paying your 50% less if you want 80% protected time for research. Having your own grant is always a good thing, and the K award system is currently the de facto gatekeeper for most cognitive specialties. It has about a ~40% (and decreasing) rate of funding.
People who don't secure K awards or something comparable by the 3rd to 4th try have a very diminished (though not impossible) chance of having any future in academia as a full time researcher driven by external grants (~10%--perhaps lower, I haven't seen a good example of this)--typically this is also the age where people start thinking about leaving around 40. However, other careers in academia remain open (i.e. clinician-educator, admin, etc.) Many researchers stay in a non-research primary role and write grants and get an R01 or two in their 50s or 60s, but they are not "continuously funded" and generally do not become "core" research staff in a department. Around age 40 is also where transition to industry happens most frequently, as this is the time where you can still have a spectacular career in industry. If you enter industry in your 50s as a lateral hire, usually you face issues relating to your peers being significantly younger. Senior management in academia do transition to senior management in industry with some regularity, but this doesn't change the content of the job prior in academia.
After K award there's further attrition between the K to R transition (~age 45), which is about optimistically 50%. After the first R01 the attrition rate slows down, perhaps to about 5-10% per decade. That said, with indirects, typically around two R01s, the total input would cover most of the institutional salary for 30 years, so 2 R01 is a breakeven point for most institutions, which is why the associate professor/tenure/hard salary line comes online between 1st and 2nd R01. This decreases attrition and at this point usually you can coast with minimal productivity or pursue riskier projects. This usually happens in your early 50s.
Compare this to a clinician's career trajectory, typically you start making 3x salary in your mid to late 40s, and if you do well saving and investing, by the time you are 55 you should be largely financially independent. At this point if you have an interest in research you can pursue some research in an offhanded way. Most people don't, though...as they prefer to say curate their real estate portfolio than getting rejected the third time by paper reviewers on material that's not important enough for most to care. Women and people coming from poorer origins also do worse statistically as they have other competing priorities that can interfere with devoting to these activities and have little direct monetary reward.
COVID is making working from home more acceptable, which likely means that institutions would be more willing to let full-time researchers to work remotely. However, for physician-scientists, not interacting with patients would not be easy even for cognitive specialties. I don't think this will change much the overall picture. The general problem is the system is being painfully selective and often the criteria are arbitrary and luck-driven. This has more or less to do with the funding climate and how poorly the labor market was designed.