I do semi-pro sports and architectural photography, which are kind of on opposite ends of the spectrum of needs. I started back in 2006/2007 and still use all the lenses I bought back then. I started out with a Nikon D80 (DX) and a Tamron 35-70mm f/2.8 lens. A decent camera for the time, and a very capable but still kit-ish lens. Not long after I got a Nikkor 70-200mm f/2.8, a Nikkor 85mm f/1.8, and a Tamron 17-35mm f/2.8-4. Since then I got a Nikon D7000 (DX) and most recently a D750 (FX). They were all major upgrades, but all the lenses still work (even though the Tamron lenses are technically DX format they work fine in FX with the 17-35 having some soft corners that are usually cropped out by the time composing and distortion correction are applied).
The D7000 and D750 with the 70-200 lens are killers for sport. I shoot the D750 with the zoom lens and keep the wide angle on the D7000 for group shots, podiums, and occasional stuff like that. The move from DX to FX did lose me some zoom, but it’s mostly made up for with the increase in megapixels. Plus the full frame sensor has much better low-light capability and less noise, which is important as many events I shoot can drag on past dusk, or go on in the rain. The full frame D750 makes my 17-35 lens an ultrawide, which is awesome for architectural photography. Even for normal building documentation it’s great to be able to fit in an entire small bathroom. With FX there’s less coverage of focus points in the frame than with DX, and I’m not thrilled about that, but for “serious amateur” that’s probably no factor.
The industry is definitely moving to mirrorless as others have mentioned already. I think Canon is jumping on that more so than Nikon. Didn’t they recently say they’re not going to make DSLRs anymore? In any event, mirroless doesn’t seem to be as good for action as a DSLR, but they’re catching up fast. They also burn through the battery faster, which can be an issue. I can shoot 3,000 photos over an entire day on just one battery. I don’t think mirrorless cameras have been able to match that.
Also as mentioned by others, manual controls are not something you have to worry about. Manual controls aren’t fake just because there’s also automatic controls. Think of them more like a dual-clutch automatic transmission perhaps. The different shooting modes (at least on Nikon) are on their own dial so if you want to stay on “M” (manual) you can just ignore sports and macro and portrait, etc. I almost never shoot manual myself though, usually preferring “A” (aperture priority) or “S” (shutter priority) where you set the aperture or shutter speed respectively, and the camera chooses the appropriate shutter or aperture respectively (and possibly also ISO sensitivity) to properly expose the shot.
All that said, with digital pictures, the whole point is that you also have more post-processing ability, especially if you shoot RAW format. I used to use Apple’s Aperture (RIP) but now use Capture One Pro for my editing and organizing. There’s also Adobe Lightroom or Adobe Camera RAW. Think of this as the development process, which lets you fine-tune the output without risking your negatives. Using only manual mode on the camera and not touching the resulting files is trying to fit an outdated usage paradigm into something that’s not meant for it.
The iPhone does a ton of background processing to make the photos look as good as possible and counteract the limitations of the lenses and sensors. That’s how they look so good from the get-go, but it’s mostly invisible and not adjustable by the end user. With a DSLR or other more “pro” digital camera bodies and capable editing software, you have control over those adjustments, and you’re expected to use them to get the results YOU want, not what the product engineers think are the best algorithms to satisfy the most circumstances. You also have more control over things that were lacking in the film days, like lens distortion correction, white balance, noise reduction, and the ability to do high dynamic range merges or focus stacking. Try to embrace the tools the technology brings rather than fighting it.