I think you’ve hit the major issue in your question. When you are new to this it’s hard to judge what is too much and so the chance of gaining an injury is increased. Sometimes an injury not only requires you to take time off PE but may mean you injure yourself in the same area more easily in the future. Time off for injury means you are not PEing and not gaining. It may even mean that the tissue has time to heal more completely than is useful for continued gains, though I’m not sure that’s easy to prove or that it’s even been reported enough times to make it likely.
Generally an advanced routine is required because a lesser routine isn’t producing results. You have to increase the stresses applied to continue to gain. Doing a routine that is higher stress than you are capable of withstanding doesn’t seem particularly useful. The Newbie Routine was designed some time ago by a physician to attempt to balance the stresses needed to grow against the potential for injury and in many cases it seems to do that effectively but of course it’s not the only route. In fact it seems too heavy for some people, who find the Linear Newbie Routine better. There are other more hardcore routes in as well and maybe they suit people better but it seems sensible to start with the minimum effort to gain at a reasonable rate and increase it as gains slow or stall.
The argument that’s often given is that there’s a limit to the amount of useful stress you can apply, so a plateau is inevitable once you hit that point. There are ways around this of course: PEing for longer periods, changing techniques, taking deconditioning breaks of several months etc.
People often resort to devices once gains slow and sometimes this helps but sometimes it doesn’t. The reason it may help is that stress is being applied in a different way or at a greater level. There are many instances of people hanging, clamping and pumping and not gaining and there are many instances of people using entirely manual methods for all their gains. Adding devices may be best seen as a route forward when there are no other routes forward.
The perception of devices can be different from the reality. For example it’s easy to get a temporary increase from a pump, especially when overpumping and causing a lymph buildup. It also feels great to be hanging heavy weights. But these feelings don’t necessarily translate into permanent gains.
The forums are littered with examples of plateaus with all method of PE, so there’s no one obvious route that ensures the best growth and the least chance of plateau. There are however plenty of examples of injury in the early months of PE. This is why we tend to stress a less is more approach as an initial route into PE but I would add to that increase quickly if gains are not apparent quickly and PIs aren’t suffering and don’t make changes if you are growing at a reasonable rate. You have to think about PE not so much as a regimented thing but as responding to the feedback you are getting.