I do not agree.
When using Total Commander I use 99% of times the right mouse button to select files, while 1% of times I use it for the context menu. So it's not a problem having to white a fraction of a second to get it when I need.
If I were using Total Commander to use context menus and standard Explorer-like features, I would keep on using Explorer, rather than Total Commander.
Having the right mouse button available to select files is much more comfortable and quick to use. An option to enable or disable this would make anyone happy and I don't think it were a so complex task to implement.
Using any combination of shift/ctrl + mouse click is less immediate, because you have to use two hands (and the keyboard).
The times when a PC mouse only had two buttons might be over, but there are still many mouses around with just two buttons plus the wheel and using the wheel as a central click is not very comfortable if used heavily and while dragging (like you do to select files in a file manager like Total Commander/muCommander).
Last but not least: Norton Commander, Total Commander and Midnight Commander have set many de-facto standards on file manager software features. Although they are old, many people are still used to them and I think that good ideas never die. The possibility to use the right mouse button to select files I think is one of those good ideas and this feature is available on all of the aforementioned programs.