question - can i install normal flourescent fitting t5/t8 directly on plain plaster ceiling?

the electrician say not strong enough wor ...cannot screw properly.
i dun really like downlights cos at the end - it cost more to put in more light points and at the same times, u turn on more downlights.

2 T8 superbright x36w =72w
where i believe it needs ard 6 downlight to get the same brightness = 6x18w = 108w