Hi Denny:
Thanks for your prompt response. Alas, yours is a common cautionary tale of the need for researching all aspects of a brand change.
Canon, like Nikon, have not unreasonably, held back on allowing 3rd parties to produce fully-compliant native RF lenses for their new bodies. As I understand it, that is for a couple of reasons.
The significant changes rendered by the new tech and especially lens interface mean that they did not want to have others produce for an evolving platform. Doing so would put those 3rd parties in a situation where the interface changed, undermining the effectiveness of their designs and compromising results. There is a mutual benefit in 3rd parties gaining authorization from the OEM.
Secondly, and not unreasonably, they wanted to develop their own platform of native lenses to support their massive investment in creating a major platform shift. Now, many have compared the availability of 3rd party lenses for Sony, so I went back and logged the release rates of 3rd party lenses for the Sony platform which began in 2010 (and is thus a much more mature market). Third party lenses started with a trickle and did not become much more frequent until at least 5 years after the initial release. Now, that would equate to more 3rd party lenses being seen for Canon and Nikon next year, which is possible. However, their development was, and still is, impacted by the world-wide disruption from the pandemic, with bottlenecks in design, production and logistics that will impact both 3rd party and OEM manufacturers.
Both Canon and Nikon have stated that they will support selected 3rd party lenses on a case-by-case basis, but in the meantime Canon is releasing a significant number of lenses, many at a lower price point, with 32 new designs on top of the current offering within the next few years. There are suggestions that there are up to 8 new lenses pending release now. I would not recommend discarding native lenses - Canon makes fantastic optics, and even their cheaper ones are of high quality and represent good value for money. Superzoom lenses, like the 18-270 you referred to, come with quality compromises, especially on a focal range band that goes from wide angle to super telephoto. You get what you pay for.
As to both lenses and body, the other significant (and arguably more important) question I will pose is: what do you intend to produce?
For example, do you want to output for social media, digital display, make small-medium prints for personal consumption, large prints, or prints for sale? Each of these poses different demands on the equipment you purchase. For example, the bigger the prints, and higher the resolution, the more MP a sensor should be, while those images for social media and even digital display are going to be massively downsized significantly so one does not need a high MP sensor.
If you have read my rather lengthy response to my respected colleague Bill (Waddizzle), you will see that I concluded that within limits the R7 works well, so much depends on what you want the camera to do for you in terms of frame-rate. As a wildlife shooter, I don't go for super high frame-rates: TBH I don't want to spend my life going through thousands of almost identical photos on a computer after shooting. I prefer to shoot carefully and get a high keeper rate - but that is an individual thing. I chose to go with the full-frame R6 bodies with their better build, battery grips, and focus + tracking system and, if necessary, I crop in by 1.3 or 1.6 factors in camera that reduce the Field of View, but reduce MP size and for my purposes that is absolutely fine - however, I am prepared to pay for that performance..
Some examples of BIF for the R6 tracking and IQ - remember these are all reduce to file sizes < 5MP:
