@awnlee jawkingYes, they have had limited success on their minimum goals, as in, "land bridge" and railroad to Crimea (Sevastopol strategic port). Siege of Mariupol discounted, they reached those in under two weeks at the start of the full-scale invasion.
Yet, they have continued to attack, at a price of over thousand men a day, ever since. And in fact, they have been rolled back even from that initial success, partly. They had to abandon (at least for now) idea of sizing Kharkiv and Odessa, both arguably *more* Russian-speaking and Russia-leaning prewar than Zaporizhzhia and Kherson ever were.
Speaking of, they had to retreat from Kherson (and that they were *allowed to* as we have learned since, was one of the greatest betrayals of Ukraine by US and partners so far; we talk about several dozen of thousand prisoners of war not taken, including a whole army headquarters...) Unironically, US direct support or not, one of if not the most successful operation of this war so far for Russia had been the retreat from Kherson, (and second was the escape from Izium, although they lost all heavy equipment there). Had those two ended with the mass surrenders that could have been achieved... well, that's water under the (destroyed) bridge.
four regions
You're dangerously close to falling for Russian propaganda in your wording, but I will accept that as rhetorical. As the situation on the ground is, they only control anywhere near 100% of one of the regions they want to claim on this, lowest of the three levels of goals, and that is the least consequential: Luhansk (north east corner of Ukraine, the regional capital is on the very south east edge of the region and was sized in 2014 already).
Donetsk region, they have painted most of the territory now, yet they're still not even close to lay siege to the Slavyansk-Kramatorsk three-headed agglomeration in the north west of the region. They claim those fortress cities they never controlled in their "peace proposal".
Kherson, they were driven out of the city of Kherson itself, along of the part of the region on the west bank of the Dnipro river. Russians pretend the entirety of the region is now their "constitutional" territory. Zaporizhzhia, they haven't ever been anywhere close to attack Zaporizhzhia city with anything else but rockets and glide bombs from a distance.
Kharkiv, they were driven out of it entirely, from effectively a siege of the city (home to one of the three principal armor factories of USSR). Although right now they again do hold a couple corners on the border and one small bridgehead over the Oskil river, they have (for now) abandoned claim on the region.
Odessa they never entered, and Dnipro (where every single ICBM of the USSR was built; they can't even service those without Ukrainians) had remained a distant goal as well.
However, when I talk about strategical failure of the Russian war effort, I mostly have their maximalist goals, and those are going far beyond territorial: now even complete conquest of Ukrainian land would still be a failure on those. Razed Mariupol alone ensures that, the unique heavy industries housed there are destroyed and so is most of infrastructure necessary for it. Even Ukrainian manpower loses are also Russian loses on this level, as those are now denied for the continuation of their campaign Ukraine was intended as a base for.
Failure to capture control over Ukrainian industrial base and population intact is the major strategic defeat Russia had suffered in this war, and that is definitive and cannot be amended regardless of any effort because those assets are either destroyed or rendered incompatible by the very war launched to size them.
Failure to deny Ukraine access to the Black Sea is less definitive, as in, it can at least in theory still be achieved through future success on battlefield or in negotiation, and so is the control of remaining territory of the regions enumerated above. Yet, it is, at this time, a complete failure on the middle level goals.
Even the limited success on the minimum goals remain contested. While it is indeed unlikely Ukraine will be able to launch major offensive maneuvers this year, I wouldn't rule out possibility of them regaining such capability in relatively near future, even regardless of continued US support (with had been less than 25% of total needs covered overall (not to say, even less of wants, but those are unlimited by definition)), despite some unique capabilities that would difficult to replace directly. I think people seriously underestimate Ukraine's dependence on US, and both willingness and ability of them to continue defense at least in absence of outside support.
What can change the calculation is US switching sides actively, and either rescuing Russia from the looming material exhaustion, or tacitly allowing China to do so (although is China willing, or only using US sanctions as a fig leaf for own policy remains unclear).