Second Empire France was a rival to Britain in first-line warships, and in early ironclads the British and French were matching each other in producing classes to rival.
Best Regards
Grey Wolf
The French fell behind massively during the age of the pre-dreadnought though.
By 1910 the French would have had at most 20 battleships in service (or reserve, I'm including the Marceau, Messina and Hoche in those numbers and they were hopelessly obsolete by this point), no Dreadnoughts, 23 armoured cruisers and 24 protected cruisers from the 1890s and most of those are obsolete and old, no scout cruisers, and no light cruisers. Many of the French Battleships are also old and of inferior design to contemporaries across the channel (namely Bouvet and her 4 'sisters' as well as the Brennus class ship, they were flat out inferior to their RN equivalents, the Majestics and Canopus classes, of which there was 9 and 6 respectively, the 3 Charmalagine class were 'okay' but small for their role and again, roughly equal to the Majestics).
The RN would have had 35 Battleships in active service, as well as 4 Dreadnoughts and 3 Battlecruisers, 35 armoured cruisers, 71 Protected cruisers (again some are old and obsolete others are not) 10 scout cruisers and 6 light cruisers. And I'm not going to count the Destroyers/torpedo boats for either side. This kind of quite frankly absurd number disparity is the big problem here. And whilst many of the protected cruisers would be dispersed across the globe, if the UK was threatened then you can bet the vast majority would be recalled home, same with the armoured cruisers. And all the battleships and dreadnoughts would be in home waters or the Med. Whilst the French fleet's split between the Med and the Atlantic coast and there's Gibraltar in the way to unify their forces.
And if France built up its fleet somehow (stopping the revolving door at the Admiralty and thus having a stable government would be a must for this), why are we then assuming that the UK would build as per OTL. This is one of the issues that often crops up in Nazi wanks. The Nazi's build X Y Z and develop M whilst the Anglo-French do EXACTLY as per OTL and do not respond in any way. If the French somehow managed to get their house in order at a leadership level and then get the shipyards organised and more built and an efficient program of warship construction started in the pre-dreadnought era (Which itself would pretty much take an act of God as the French ship building industry from the 1890s onwards was a mess) then the UK is not gonna go "Oh this is fine." And not react. The UK could afford and had the facilities to build far more ships. So you'd probably see 9 Majestics, 9 Canopus, 9 Londons etc etc etc and these are numbers that the French simply can't match because they don't have the infrastructure for it.
As an example it took the French 6 years to get this ship into service
https://en.wikipedia.org/wiki/French_battleship_Carnot and the fastest built of her half sisters was 5 years. Another far worse example was
https://en.wikipedia.org/wiki/Marceau-class_ironclad laid down 1882, completed 1891.
the UK built the Majestic class within 2 - 4 years, all 9 of them, thats how efficient the UK's shipyards were. And if you build up a fleet to challenge the RN and threaten the country, the UK could afford to do that again and again if you start a building race with them, and its a race that France would loose. They don't have the shipyards, or slips to build enough ships to challenge the RN at any level.
Looking at small craft in service you're also talking the RN having 180 odd destroyers of varying size and quality, with 64 of those being more modern ships that would be more recognisable as a WW1 type destroyer rather than a large torpedo boat destroyer type.
France had 55 destroyers, most of which were the older Victorian era torpedo boat destroyer type design and no more modern WW1 type destroyers, the large swarms of torpedo boats the French had made during the Junne Ecole period were largely gone or horrifically obsolete with a bare handful of later designs, namely the 5 strong Cyclone and 6 strong Mistral class being anything remotely useful in the modern era and even then they're small, coast defence craft, not offensive units.
Also this is the Royal Navy that was shaken out of its malaise by Fisher and his innovations and time in command of the Med fleet. By 1910 the RN was more than ready for a war with anyone.
This vid gives a good breakdown of the French Battleships of the period we're talking about, and by 1910 the French would have all four Libertie's in service and them, along with the 2 Republique's are the most modern and capable French Battleships. Facing them are 4 Dreadnoughts, and everything else, the King Edwards and Lord Nelsons would be more than a match, and there's 8 King Edwards and 2 Lord Nelsons. And there in theory should be 19 French Battleships as the Iena blew up in 1907.
So I hope this gets across the number problem the French face, and they have to defeat the RN in the Channel, and in the Med, to stand a chance.