I think there are two main reasons why Ukraine is holding back on the offensive.
First, the Russian military has been able to push back is because they've had a year to dig in. Minefields, trenches, and various defensive obstacles are tough to roll over. Especially in winter, when foliage is low and dug-in positions are easier to spot, the cluster munitions will be highly effective against dug-in infantry or Russian units on the attack.
Second..
"Late Monday, reports began emerging that the Kremlin was staging 180,000 Russian troops along the eastern front in the Donbas"
"Moscow has amassed 120,000 troops along the Lyman-Kupiansk corridor and 50,000 soldiers in and around Bakhmut"
https://thehill.com/opinion/national-security/4081097-the-russians-are-coming-why-putin-might-be-massing-180000-troops-near-the-donbas/
But to do this, Putin has put Russia into a militarily precarious position.
"the Russian 58th Combined Arms Army, which usually deals with security in the Caucasus region, is operating in Zaporizhzhia Oblast"
https://www.pravda.com.ua/eng/news/2023/07/6/7410053/
The 58th CAA is primarily responsible for peacekeeping duties in the conflict between Azerbaijan and Armenia.
"Azerbaijani state media has in recent days made increasingly frequent mentions of a possible new military operation in Nagorno-Karabakh, as reports of severe food shortages in Nagorno-Karabakh mount."
https://oc-media.org/azerbaijani-state-media-warns-of-inevitable-military-operation-in-nagorno-karabakh/
"Velyka Novosilka, Donetsk Oblast, the positions are held by the 5th Combined Arms Army and the Marines"
https://www.pravda.com.ua/eng/news/2023/07/6/7410053/
"Most of the marines of Russia's 61st Naval Infantry Brigade, which is stationed near the recently expanded border with NATO in northwestern Russia, are deployed to Ukraine, where they have taken heavy losses."
https://finance.yahoo.com/news/russia-accepting-risks-dropping-guard-145002646.html
Where is the 5th CAA headquartered?
"Russia transferred some two-thirds of the combat forces assigned to its Eastern Military District from their bases in the Far East, roughly 6,200 miles away, to central and western Russia and southern Belarus."
https://finance.yahoo.com/news/russia-accepting-risks-dropping-guard-145002646.html
"Airborne regiments are mainly holding the defences around Bakhmut"
https://www.pravda.com.ua/eng/news/2023/07/6/7410053/
Remember that Airborne units are normally part of the strategic reserve and a few companies were recalled to defend Moscow against Prigozhin.
"Up to two companies of Russia’s 76th Airborne Assault Division got to Moscow by Il-76 transport aircraft"
https://kyivindependent.com/military-russia-redeploys-airborne-troops-from-ukraine-to-protect-moscow-from-prigozhins-mutiny/
The argument against "unexploded cluster bombs" are likely by Russian-compromised individuals or just plain naive "useful idiots". Terrain denial by landmines is already in the millions. The people arguing against the cluster bombs need to consider the crimes already committed as well as the lives that have and will be lost.
However, if someone really wanted to give Ukraine an anniversary present, long-range HIMARS with F-16s equipped with HARM missiles, would be nice. Or.. if someone wanted to gift and early Christmas..
"Erdogan says Ukraine ‘deserves NATO membership."
https://www.nytimes.com/live/2023/07/07/world/russia-ukraine-news