Any LORE explanation to why things are far lower level on 5e?
I mean, on 2e D&D Strahd von Zarovich is a 16th level necromancer, capable of launching tier 8 magic and with far nastier magical abilities. On 5e, he can only cast spells up to tier 5, no vampiric level drain, and to name SOME abilities of him and note that on Barovia, magical weapons are rare. Finding a +2 weapon on a Ravenloft campaign is not easy. - Ravenloft - Domains of Dread.
On 5e, he can only cast tier 5 magic and note that tier 5 magic on 5e is far less deadly than 5th tier magic on 2e. And if you look into Strahd lore, he was considered before the "fall" a mage of "mediocre" skill, a lv 5 mage which many people consider a fully fledged wizard on 5e. And i an not even talking about the spells which he knows on 2e, his contingency, clone, finger of death, antimagic shell, limited Wish, force cage, teleport and so on. All nasty spells which in the hands of a good DM can easily end a mid to high level party.
And is not only casting. Tiamat stats seems honestly seems weaker than DEMON LORDS on previous editions. Mindflayers seems like a common mid level creature and so on.