Have been detecting since 1982 and if your not digging some junk with your finds, your not seriously detecting and may be discriminating too much for what ever you are looking for at or lower than pull tabs.
One machine I run is a BH Pioneer 505. One advantage I see in the multi-tone machines is I can run zero discrimination and yet still rely on 4 tones to do some segregating. The 505 is also the only machine I have that uses tones and digital display to give a HINT of what you may have found before digging. Can't say I put all my faith in the display, not because it don't work but it can be fooled now and then. I say hint because not all pull tabs for instance are made of the same aluminum alloy as another and can find now and then that one part or the other is missing or folded back over the pull ring changing how it detects. Even with coins, how they lay and how oxidized they are will determine how they detect. Dry and wet soil and those with high mineral or irons can test you and machine. What you are going to discover is you may dig a pull tab and wonder why it did not quite tone and or display as one when others do and so on with other things. These machines are set up for the most likely metal alloy content you will encounter and those you want to keep with as little effort as possible required to electronically discern them. The Zinc and Copper pennies being a good example of different alloy content and what most likely would be encountered though some folks would prefer to not bother digging and or keeping the Zincs.
These Tone Machines are not like old school where those of us learned and still hunt by sound, seeking particular variation and duration of it through the coil swing, not by bells, whistles, and teleprompters
. My old Garrett Freedom II in the pin point mode will tell me almost 100% of the time that I have found an aluminum beer or soda can. It's not a listed or promoted feature of the machine or is it in the instruction manual but I did eventually put both sound and can together by the distinct sound it made. Why it does it I can not explain and especially when pin point is all metal and should be one sound for all metal.
Something you may try is the small 4" coil in trashed out areas. You may lose a little depth but will hit on smaller items and not have so many things under your coil at once to figure out. I think you have the right attitude though, jump in with both feet and and learn it, and your machine will not end up sitting in a closet. Too bad though you had to buy one of them pin pointers. More batteries and stuff to pack around, keep dry, and get in the way. My 505 pin points like a good Bird Dog. It has the All Metal Mode but you use the Ground Trac which is like a ground balance with it to sort of speak, dial it in on the spot if you need to be more precise. I don't think the Lone Star came with Ground Trac but has the All Metal mode. Have more than once enjoyed my 4" coil in trashed out camp sites and other places and would not part with it.
As for mostly finding modern, you need to keep in mind how many years people have been detecting and where at before you. Then figure in places people used to be able to detect and can no longer. It's not that there are no coins to detect for, it's that the older in the best available places have pretty much been gone over and many times. Construction, land closures, housing developments. The silver coins tend to stand out when dropped and people are more likely to see and pick them up before bothering with a penny. The area I'm at is hunted a lot but I have managed to find one wheat so I feel fortunate.
If you think it's hard trying to find old coins, you should try your hand at detecting for natural gold (a whole different kind of detecting). I'm in Gold country (very worked over) and can find tiny pieces of lead and copper bullet and bird shot fragments but I have yet to find a nugget or flake of gold electronically. I even use two different tiny pieces of gold as my out in the field test pieces to check my settings. The general rule is if you can find lead, you should also find gold at about or the same size IF it is there.
The way I look at it, most of us will never get rich doing this stuff so you have to have a love for it first and be content there is anything in the ground to dig for as it all could be taken away tomorrow.