We are, they are highly experimental and quite expensive. Tidal power is not trivial because you know, salt water pretty much destroys any machine out in it. They also only work in very specific areas of the coast with high tidal flows.
Roses are also variable both through their cycle and from day to day. They stop generating completely twice per day but they are predictable though.
Wind turbines also don’t have ‘short lifespans’. The irony of suggesting building tidal turbines because wind turbines have a short lifespan. It’s a shame there isn’t a face palm emoji here.
Sure you can build tidal lagoons like the one which was proposed in Swansea but again they only work in places which exceptionally high tidal ranges (different to flows) and it’s not like diverting a river estuary doesn’t have any wider impacts. It’s also unproven so it would be a complete stab in the dark and definitely not cheap.
essentially arnt a lot of the tidal generators essentially like giant wind turbines anyway.... just under water.... therefore a lot of the failure parts would be comparable... albeit operating in a corrosive environment.
not knocking them however, tidal power is predictable and reliable and is certainly one of the solutions which need to be used.
imo the problem is we have had it easy for so long....... oil is pretty fantastic stuff, its just incredibly damaging. renewables are far better over all but there is no doubt they are not as easy a solution as just burning oil products. No one renewable is going to cut it, but all of them together i believe can...... and if they cant then we are a bit knackered .... or more accurately our kids / grandkids probably are.
as for maintenance (aimed at Nasher)..... sure they need some maintenance... and a damn good job too looking at it practically. With AI going the way it is, we are going to need jobs for people and engineer is a pretty good option.
but what about all the maintenance of nuclear / oil / gas powerstations and refineries.
Hinkley point's construction bill would cover a lot of renewable generation, and that is including maintenance. (not that i am saying we do not need nuclear... we likely do at least for now)
pretty sure wind turbines have around a 30 year lifespan, at which point most of the end of life parts can then be reused, either in construction or just mulched up and recycled that way.