I mean, those takes are clearly hyperbole, but there is a grain or truth to it. Bear with me: Let's assume for a moment that Trump's peace plan goes through mostly as proposed and that the US security guarantees to Ukraine prove reliable over the following years - what would Russia have accomplished in the end, compared with the status quo ante in January 2022?
They would have captured the third of Donetsk/Luhansk which they were still missing back then, they would have taken a small strip of mostly depopulated and not very resource-rich land between the Donbass and Crimea, and they would have gotten Ukraine to officially acknowledge the secession of Crimea and the Donbas. Ukraine, on the other hand, would have defended its autonomy and could join the EU and now has US security guarantees which prevent Russia from pushing them around or taking more of their territory in the future. Meanwhile, Finland and Sweden have joined NATO and NATO is now much more alert to any Russian actions in general. The West is re-arming, which according to the Russian theory of the case forces Russia to keep spending bigger sums on its own military in the coming years than they would like to.
All in all, this outcome is still a "win" for Russia (rather than a loss, lmao), but it's a far smaller win than what they were going for. And it would indeed be valid to question whether such an outcome was actually worth the death toll and the economic disruption. The answer is probably a "yes", but only narrowly so.
On the other hand, if the peace plan ends up being trash, Ukraine gives up its most fortified positions in the Donbas (Kramatorsk/Sloviansk), Russia keeps attacking and the US goes back on its security guarantees, leaves Ukraine high and dry, then this plan would be a huge boon to Russia. So long story short, we're back at my previous point that the specifics and the reliabiltiy of those security guarantees will be the crux in all of this.
The main benefit to Russia is economic, they're selling oil and gas at steep discounts, and they'd see relief from sanctions that are having a significant impact on the Russian economy. They'd also see hundreds of billions in assets unfrozen, which I'd expect to see them move out of Western control.
The second question is how Ukraine responds to the effective loss of territory. I'd expect to see Russia continue to intervene in Ukraine in an attempt to influence their electoral results. It's not unthinkable that Ukraine might end up like Belarus in 10-15 years time.