There's definitely been a bit of a shift in the last ~4 weeks on the eastern front. Syrskyi deserves a lot of credit for some shifts when he took over from Zaluzhnyi but imo the two biggest differences under their control are technological. Zaluzhnyi was kind of stuck between between two worlds as his force evolved. He had a lot of legacy soviet equipment and soviet era officers in the beginning but started to inherit more NATO standard equipment and NATO trained forces over time, which he put to fairly good use but never really had the critical mass of men and equipment to sustain offensive momentum. Did a pretty excellent job identifying Russian collapses and leaning the fuck right into them (Kherson and Lyman) to turn them into routs that returned signficant land back to Ukraine, but didn't have the capability to exploit Russian logistics weaknesses broadly enough. A lot of this can be blamed on western aid getting slow rolled tbh. If the Biden admin had just opened the firehose of what was promised and let him go to work, things probably go quite differently. But having aid slow rolled, and always with pre conditions really hampered his ability to fight.
Three things have changed pretty massively over the last ~6 months. Two are due to Ukraine filling it's own equipment gaps at two different and very important levels and one a product of Russian tactics and force generation over what is now a long period of time.
First is Ukraine developing their own long range attack drone & missile industry from reverse engineering other people's gear (Turkey's definitely, unexploded Iranian shahed's definitely, and getting a long look at things like Storm shadows and ATACMS didn't hurt at all either) which removed the aid requirement of not attacking targets in Russia proper. They've done a really good job at disrupting Russian supply lines and making what was already a logistics challenge into a logistics nightmare.
Second is the advent of the fibre optic drones:
The Russians were fairly adept at electronic counter drone warfare and the hit rate of FPV drones was okay from a Ukrainian perspective, but low enough that it was hard to plan around their use to protect Ukranian positions, or provide any sort of support to attacking manuevers. Well...the fibre optic drones, that yes, just run on a big fucking spool of fibre optic cable connected to a transmitter are more or less immune to jamming and are very, very reliable. So Ukie commanders, who have these in large numbers now, have been using them as close air support for counter attacks similar to how US forces have traditionally used Apache's or A-10's.
The third is that the Russian infantry is getting really old, really quickly. This is the problem with meat wave tactics, you're always in the need for more meat and they've largely run out of younger recruits. Among contract recruits, the average age of KIA's over the last 6 months is over 40 now. This isn't a force made up of Russia's strongest young men anymore. They're dead or maimed. It's their fathers taking the ever growing sign on bonus and joining the fight now. For comparison, the US Marines won't even accept a recruit over the age of 28. Being a soldier is like being a professional athlete from a timeline standpoint. 33-35 yrs old is ancient. More than half of the Russian infantry is 35+ and it's quickly getting older.