The trouble with Dr Who is that it is kid's fantasy dressed up as sci-fi. These days I feel like I'm watching the truly terrible Merlin rather than so9me sci-fi.
In story telling ultimate power must come at a price otherwise you can magically extract yourself and your friends from any peril.
Time travel is supposed to be fraught with difficulties and potential universally apocalyptic paradox scenarios etc... These things should constrain the protagonist's ability to solve a situation and thus force some clever solution to be thought of rather than 'magic'
For example if it is OK for him to dump 20th Century military hardware in the middle ages, then surely it is acceptable for him to use that same hardware (or future military hardware) to defend humanity.
In fact, if time travel is so non-trivial that he doesn't have to worry about paradoxes or ripping the universe to pieces at the quantum level or whatever then a great many of hius problems can be solved by simply going back in time & removing the baddies at birth or going to the future and returning with OP future tech for the potential victims of evil to defend themselves.
It doesn't have to be realistic, but it should at least try to be internally consistent. The trouble is that next time a 20th Century tank (or 24th Century armed flying car) will solve the problem that's what I'll be erroneously expecting.
Series 1 of renta ghost was more consistent than this garbage. I'm forced to watch it because the missus does. At least it now has Michelle Gomez in it I suppose. I can watch her hamming it up all day.