It is only backwards compatible two generations, occasionally something slips at the LTO trust (or wherever those things are designed) and you get three generations. But if I have a basement full of LTO1 tapes no currently manufactured drive will read them. I would have to buy a used drive and the drives were never really made all that well. Better than the DAT drives one company I worked for used for some of their backups. But still mechanically very complex with many many small delicate plastic parts that wear out quickly. Those DAT drives were super delicate and also suffered from the same generational problems LTO does. We had a bunch of DAT1 tapes somebody wanted data from but had no working drives to do so. All our working drives were newer DAT3 and 4

That was always the hard part to justifying tape backup. the storage is cheap. but the drives are very expensive. And never seemed to last as long as their price would warrant.