When people talk about "Stalinism," they usually mean one of 2 things:
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Marxism-Leninism, the synthesis of Marxism with the advancements made by Lenin. Stalin synthesized Marxism-Leninism, so this gets called "Stalinism" despite Stalin's minor contributions compared to Marx and Lenin.
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The policies of the USSR while Stalin was General Secretary of the CPSU.
The former, Marxism-Leninism, is the largest tendency of Marxism by far. This is because it has proven its utility in practice, establishing socialism in many countries with varying local conditions and contexts. Lenin's contributions to Marxism are near universally accepted by Marxists, and Stalin did not change from them in synthesizing Marxism-Leninism.
The latter, Stalin's policy positions, are largely either contextualized and explained, rather than actively defended, or are genuinely good feats. For example, under Stalin, literacy rates skyrocketed from ~30% to 99.9%, life expectancy doubled, education and healthcare were made free at all levels, jobs were guaranteed, and much more. Genuine faults, like criminalizing homosexuality, are recognized as such by Marxist-Leninists.
As Weng Weiguang says, The Evaluation of Stalin is Essentially an Ideological Struggle. Marxist-Leninists don't idolize Stalin. At the same time, Stalin synthesized Marxism-Leninism, and oversaw the world's first socialist state during its most turbulent period. The CPC rates him as 70% good, 30% bad, and this rating is roughly orbited by most communist orgs. Those who denounce Stalin entirely, also denounce the USSR, and existing socialism.
Stalin was a committed Marxist-Leninist, and oversaw the world's first socialist state for the overwhelming majority of its most tumultuous period. He was no saint, but at the same time was no monster either. He is remembered by liberal historians as far worse than comtemporaries like Churchill who in actuality were far worse than Stalin.
As Nia Frome says, we can either distance ourselves from Stalin, and by extension the USSR and actually existing socialism, or we can fight back against bourgeois narratives about Stalin and the USSR, acknowledging their faults while being able to uphold their tremendous successes as examples of the possibilities of socialism in power. Historical nihilism, and throwing Stalin and by extension much of the early soviet union under the bus, was ultimately what allowed for liberalization within the USSR and partially contributed to the death of socialism in eastern Europe.
If you want an intro to Marxism-Leninism, check out my new basic ML study guide!