As primarily an amateur, I never liked the DOF profile of full frame even in the film days, and I sure don't like the size and cost in the digital era.
A general rule a full frame camera can match the depth of field of a crop body. The full frame should be able to match the depth of field, angle of view, subject distance, and overall image noise of the crop body (there are boundary cases where this isn't true, such as very long lenses on a crop body).
Absolutely it can, at a higher cost and weight.
There's a difference between what's possible, and what's practical to do with items you can buy from a typical camera store.
This generates some practical differences between full frame and crop.
For instance, suppose I want a very narrow angle of view. The longest lens I can find at B&H is an for my full frame Canon DSLR is an EF 800mm f/5.6L IS USM Lens (about $13K).
If I put that on my Rebel SL2 1.6X crop body, I get an even narrower angle of view. Yes, I could crop the image from the full frame, however that results in fewer pixels than if I had used the SL2. (A full frame 50 megapixel image cropped to 1.6X is about 19 megapixels, the 1.6X Rebel SL2 body is 24 megapixels).
Therefore, if you want a very narrow angle of view, you get a bit more with a crop body than a full frame. (Yes, I could put a teleconverter on the full frame, but I could also put a teleconverter on the crop body).
This is an example of an situation where the crop body makes it easier to get the shot.
It is incorrect to say that full frame requires you to use shallower depth of field.
No one said that. My point is that I don't want to use the shallower DOF so why should I pay the financial and weight penalty to use part of the shooting envelope that I don't like.
Some people uses phrases like "full frame gives you shallower depth of field". I think such phrases
imply that if you shoot full frame, you
will get shallower depth of field.
I think we both agree that this isn't the case. Full frame only gives you an option for shallower depth of field. In many circumstance, very shallow Depth of Field is neither needed nor wanted.
The advantage of the full frame is that it generally offers the option of shallower depth of field.
Here is the issue: if you generally like the way full frame looks at f/2 (or better yet at f/2.8 where a lot of full frame constant zooms are) there is no reason to pay for all that extra weight and cost.
F/1.7 m4/3 system images looks a lot like f/2.8 on full frame, yet costs maybe 1/3 of what full frame costs on a system level and is far more compact. Also, the smaller sensor lets m4/3 do things FF can't with respect to image stabilization, in camera processing, etc. all at affordable price points.
Yes, there are certainly advantages to smaller formats.
As with many things, it's providing the right tradeoff. Lighter weight and lower cost, but you lose an option of shallow depth of field. If you don't need/want the depth of field option, it may be an easy choice to make.
I had a corporate shoot yesterday where I delivered 50 megapixel images to the client. They don't need 50 megapixels, but the PR people who are the decision makers loved the idea that they could zoom in and see lots of details. In terms of getting hired, the primary factor is making the client happy. If 50 megapixels helps accomplish that, I'm going to shoot 50 megapixels on a full frame. That's a situation where full frame is helpful.
I also shot some of their buildings lit up at night. I Used a tripod with a long exposure at base ISO. By shooting at base ISO, I got a little bit more dynamic range than if I had used a crop body. This made it a little easier to process the files.
Similarly, some of the shots were of room interiors, where we wanted to include the view out the window. Maximizing dynamic range made these images easier to get.
Clearly, these are unusual cases, but they are an example of a situation where a full frame body is a little it better than a crop body.
One of the issues is that the same ISO and/or f/stop will yield different looking results with different sized sensors. if you shoot a crop body with the same ISO and f/stop as a full frame, you will likely get more depth of field, and more noise. On an APS-C body, you would need to open up a little more than a stop (and reduce ISO) in order to get results similar to a full frame.
The real benefit of FF is wide angle shallow DOF (not achievable in crop sensors) and very high ISO/low light shooting.
If you are not in those envelopes, you are better off with a crop sensor camera.
Whether or not you are "better off" with a crop sensor camera will depend on how important the various differences are to you. If you are shooting in a studio with a large budget, then weight and cost may not be as significant as the ability to occasionally have shallow depth of field.
If you regularly spend hours hiking in the wilderness to get a shot, then lighter weight may be a tremendous benefit.
it certainly seems as if a crop sensor is the right choice for your needs. I don't think it is the right choice for everyone.