Israel Today, citing a former IDF general, says that Israel lost the ability to build an effective army and have become a one-dimensional air power that cannot win a war on its own
Don't be too optimistic, Israel still has overwhelming firepower and manpower advantage. They can just shell Gaza until there is no more buildings standing anymore, and then send the troops in. Losses would be still high, probably.
Loss will definitely be high in such scenario. Bombarding a city to rubles rarely work to the advantage of the invader. It didn't work in German favor during Battle of Stalingrad. It didn't work in British's favor during Battle of Caen. I doubt it would work in IDF favor here, especially against people who have a lot of explosives and nothing to lose.
But yeah, it's going to be ugly, especially consider how little IDF care about collateral damage.
The difference is that in those battles sides were pretty evenly matched in terms of firepower. In our case Israel hold an overwhelming advantage. They have an advantage in the amount of explosives too.
For sure, traditionally Israeli military is very loss averse, so if things go as well as most people expect then it's not going to be a long operation.