First of all what you’re talking about is not ‘seasonal mechanics’ but the ‘LP reforging’, seasonal mechanics would be in relation to in-cycle content, but it’s a core addition first of all and we don’t have any seasonal content, only new gameplay additions currently. To clear that up.
As for the LP reforging itself: It’s not penalizing. You had no way to make a worthless item for you (a 1-3 LP depending on your personal progress) into a potentially better item. This re-introduces value to already de-valued drops, which is overall good.
Next up there simply was nothing before that, so it’s a extra option to take, with a extra potential positive outcome.
This is a net-gain, you don’t loose anything.
Thirdly, if you guarantee a positive outcome it then causes the items that actively drop to loose value, which isn’t a positive but a negative.
One option to alleviate this is by introducing a long-term progression system for it instead, rather then the indiviual re-roll chance you acquire a form of power which accumulates with each LP you put in (could be general or specifically limited to that specific unique base) and then later on when acquiring enough you go and craft LP directly with a 100% chance onto an item.
Personally my preferred method as you’re right, it’s another high-RNG mechanic which could or could not screw you over, and I personally prefer solid gradual progression.
But in no case is it a detriment unless you look at it with the grand picture of crafting and progression, and even then unlikely to occur for now unless specific examples are provided why that would be the case.
As a last reminder: If you put your best item inside while having nothing similarly good or better available then that’s your own fault. A miniscule amount of brain power to not do something like this is a given to expect. We’re not talking about honest mistakes here but at best not reading or comprehending… and at worst not thinking at all what it means to use it with such an item as it specifically states the likely outcome.