Our theoretical framework, allowing matter creation (*) provides a possible origin for the universe (without the need of a Big Bang).
If you look at the typical composition of a star today, you will find that it is mostly (99%) hydrogen.
We know that a star burns hydrogen into helium, and therefore the relative fraction of hydrogen in the star's composition decreases annually by a specific rate (let's say 0.0000001%). That means that a star might have an average lifetime of 1 billion years, before its composition changes and it has only small fraction of hydrogen left.
If the universe were created slowly (by a slow process, such as spontaneous particle creation would be), then stars would burn out while they are being created; In other words, we wouldn't see stars that are mostly unconsumed hydrogen, but instead, stars that are mostly already consumed helium, with slow rates of hydrogen being created continuously.
But that would lead to stars having a drastically different composition: instead of 99% hydrogen and 1% helium, we might see 1% hydrogen and 99% helium. That is why I believe a "slow creation" of the universe to be unlikely.