Judging my professional experiences, the simulator and a lot of test benches have always saved my development time...
I think
professional is the key. I started playing with FPGAs when I retired so, say, 15 years ago. At the time, WebPack ISE was free but it didn't include a simulator (IIRC). I am just a hobbyist, I can't afford to buy toolchains. I had to come up with other ways to debug and test system integration. I took an approach that worked when I messed around with SBCs using chips like the 8085. Scope, logic analyzer, single-stepping, not-very-clever code, etc. It probably wasn't as productive or maybe it was, I didn't spend time creating test benches which can have as many problems as the VHDL.
Some time back, about the time Vivado was released, the simulator became free with WebPack ISE and Vivado. I'm not sure when the simulator was added to WebPack but it has only been in the last very few years. But I have 15 years of doing without the simulator so it's not like I would miss having it.
There was/is a Linux oriented simulator but I was never sure it would understand Xilinx primitives. Sure, it would understand bare bones VHDL but probably not the PLLs, DCMs, BlockRAMs and such. In any event, I wasn't sure I would get much benefit so I never bothered.
Now, the Vivado ILA, that's a tool! It gets right down to where I like to work. Logic created triggers, actual signal transitions, etc. Alas, it takes some effort to get the constraints file sorted out. It always looks so easy in the tutorials!
Even given ILA, I still fall back to lots of LEDs, 7-Segment Displays, single-stepping, breakpoints, the same stuff I used on SBCs starting back in '76. Modern boards don't always have enough IO on headers for a reasonable logic analyzer so I plan to actually learn how to use ILA. Sometime soon...
My approach is clearly limited to CPUs with simple memory interfaces. I'm pretty sure it won't work for a DDR3 interface. But it doesn't have to! There is a memory controller core included with Vivado. All I need to figure out is the interface requirements - unless I use the free MicroBlaze IP then everything is sorted. There's a lot of free stuff with Vivado!
There's a significant difference between what professionals can use and what struggling retirees can afford.